Article by:

John Lorenzo

Introduction: Manganese played a significant role in the lamination problems that plagued WWII Jefferson nickels because of how it behaves during melting, oxidation, and mechanical working of the wartime alloy. When the U.S. Mint substituted silver and manganese for nickel in 1942, they created a ternary (i.e., three) metal alloy system-Cu-Ag-Mn (Copper/Silver/Manganese)-that was never fully compatible metallurgically. Manganese has a strong affinity for oxygen, far stronger than copper or silver, so even under controlled furnace conditions it readily forms oxides during melting. These oxides do not dissolve back into the metal; instead, they remain as hard, brittle particles suspended in the alloy. From the moment the strip is cast, the metal already contains microscopic inclusions that resist bonding with the surrounding silver (Ag)/copper (Cu) matrix.

As the strip is rolled to final gauge, those manganese-rich inclusions become stretched into long, thin stringers (i.e., a stretched area of impurities). Because the oxides and sulfides do not deform plastically, the surrounding copper-silver matrix flows around them, elongating them into continuous seams. These seams are mechanically weak: they interrupt grain boundaries (i.e., metal junctions), create discontinuities in the metal's internal framework, and act as pre-existing fracture planes (i.e., crack paths). Even before a blank is punched or a coin is struck, the alloy contains built-in layers that are poorly bonded and are prone to separation.

During striking, the high-pressure metal flow further concentrates these manganese-oxide stringers near the surface, where the metal is under the greatest strain. This is why war nickels often show fine, parallel streaking-evidence of the elongated inclusions aligned with die flow. The surface enrichment of manganese, combined with the brittle nature of its oxides, creates a thin zone where the metal is especially vulnerable. Any post-mint stress-circulation wear, pocket impacts, or even mild thermal cycling in coin circulation-can exploit these weak seams, causing the surface metal to lift, peel, or flake.

Over time, the result is a lamination behavior where the problem is not simply that manganese is present, but that its chemical tendencies and mechanical incompatibility of Mn with the Cu-Ag matrix creating inclusions the U.S. Mint could not eliminate. The wartime alloy was a compromise born of necessity, and its internal flaws were locked in from the moment the strip solidified.

SEM/EDS and XRF complement each other almost perfectly when you're trying to understand manganese-oxide stringers (see the Definition section) or other elongated Mn-rich anomalies on wartime alloys. SEM gives you high-resolution imaging showing the actual morphology of these features-whether they appear as thin seams, nodules, or discontinuous oxide trains running along worked grain flow. Backscattered electron (BSE) contrast makes Mn-oxide phases stand out clearly because they have a different average atomic number than the surrounding Cu-Ag matrix. Once you locate them visually, point EDS or line scans can confirm their chemistry, showing Mn with associated oxygen, sometimes accompanied by minor environmental contaminants such as S (sulfur) and/or Cl (chlorine) depending on the specific oxide/sulfide/chloride mixture.

XRF then gives you the bulk context that SEM/EDS cannot. Because XRF penetrates a much deeper and wider volume than SEM/EDS, it captures the overall Mn content and flags whether the alloy contains enough manganese for these oxide seams to be metallurgically expected. Even though XRF cannot spatially resolve the stringers, it confirms that the anomalies you see under SEM are not contaminants or isolated defects-they're the surface expression of a broader Mn-bearing system within the coin's alloy. When you combine the two methods, SEM/EDS tells you where and what the anomalies are, while XRF tells you how much manganese is present in the bulk and whether the observed features fit the expected alloy chemistry. Together, they give you a complete, non-destructive picture of Mn-oxide behavior in these coins. We explore these XRF and SEM/EDS assay differences in this paper.

Analytical Methodology

SEM (Scanning Electron Microscope) equipped with EDS (Energy Dispersive X-ray Spectrometer) can capture detailed images and identify elements simultaneously on the surface of coins. For imaging, SEM is widely used since it needs minimal sample preparation and produces excellent resolution, unique contrast, and a large depth of field. When paired with an EDS system, elemental information of the imaged area can also be derived. SEM/EDS is ideal for imaging and elemental analysis applications requiring higher resolution than optical microscopy and identifying elemental make up (1).

In SEM, an image is formed by scanning a focused electron beam, usually with energies of 1 to 20 keV, across a sample and detecting the ejected secondary or backscattered electrons.  The incident electron beam, when imparting energy to the sample, can cause emission of x-rays that are characteristic of the sample atoms. The energies of the x-rays are characterized (3).

The typical spatial resolution of SEM imaging is about 5-10 nanometers.  SEM-based EDS is primarily a qualitative technique providing data for an area only about a micrometer in diameter and a micrometer deep (1).

The strengths of SEM/EDS lie in its ability to provide rapid, high-resolution imaging, and enabling quick identification of elements present. Its excellent depth of field and versatility as a platform supporting various tools make it an asset.

XRF has some advantages over SEM/EDS analysis. X-ray fluorescence (XRF) offers truly non-destructive, in-situ analysis of a coin's elemental composition without the need for high vacuum conditions or extensive sample preparation. Unlike SEM/EDS, which requires placing the specimen inside a vacuum chamber, handheld or benchtop XRF instruments can rapidly probe coins in their entirety-preserving patina, surface treatments, and historical residues. This makes XRF particularly well-suited for museum or field studies where maintaining the artifact's integrity is paramount. Additionally, XRF's larger analytical footprint averages over a broader area, reducing the risk of misinterpreting localized inclusions or surface contaminants as representative of the whole alloy.

Beyond logistical conveniences, XRF typically achieves superior sensitivity for many trace and heavier elements (e.g., Sn, Pb, Ag) that are critical for distinguishing minting practices.

The deeper penetration depth of keV-scale X-rays means XRF samples slightly below the surface, offering a more bulk-reflective composition than the sub-micron interaction volume of SEM/EDS, which mostly captures only the very topmost layers. This bulk perspective improves statistical reliability when comparing coins across collections or establishing provenance based on minor alloying additions-core to numismatic metallurgy research. The main disadvantage of XRF is that many XRF devices if not analyzing in a vacuum chamber cannot pick up the lighter elements like sulfur and chlorine (i.e., two of the most common environmental contaminant metals found on almost all coin surfaces in particular for coins a century old or older) whereas SEM/EDS which must operate in a vacuum chamber can detect these lighter elements.

Table 1. Pre-Screening XRF Analysis of Coins #1-#3 (Surface Triplicate Analyses: Replicates (Rep) #1-#3) *: Copper (Cu), Manganese (Mn), Zinc (Zn) & Silver (Ag).

Coin	Rep*	Cu (%)	Fe (%)	Ni (%)	Mn (%)	Zn (%)	Sn (%)	Ag (%)	Pb (%)	Se (%)
1	1	54.45	ND	ND	8.21	0.12	ND	37.08	ND	ND
	2	54.22	ND	ND	8.14	0.12	ND	37.37	ND	ND
	3	53.80	ND	ND	8.29	0.12	ND	37.66	ND	ND
2	1	53.76	ND	ND	6.01	0.42	ND	39.48	ND	ND
	2	53.73	ND	ND	5.35	0.38	ND	40.10	ND	ND
	3	52.87	ND	ND	6.56	0.39	ND	40.04	ND	ND
3	1	54.22	ND	ND	8.10	0.39	ND	37.21	ND	ND
	2	54.47	ND	ND	8.21	0.13	ND	37.12	ND	ND
	3	54.34	ND	ND	8.84	ND	ND	36.58	ND	ND

*Three total random target points were selected on both the obverse and reverse. The Red Book alloy composition is 56% Cu, 35% Ag & 9% Mn. Zinc at 0.12-0.39% is fully consistent with trace Zn naturally present in copper refinery feedstock and residual brass equipment contamination.

Overall Microstructure Assessment

Sulfur & Chloride Incompatibility in Jefferson War Nickels

Sulfur and chloride contamination interact with the wartime Cu-Ag-Mn alloy in ways that amplify the weaknesses manganese already builds into Jefferson war nickels. The alloy begins this delamination process with manganese-rich oxides throughout the metal-brittle, non-metallic phases that never fully bond with the surrounding matrix. These inclusions are the root cause of the series' chronic lamination issues. When sulfur or chloride is introduced later in the coin's life through environmental exposure, they don't create new manganese problems from scratch, but they do exploit and accelerate the instability of those Mn-bearing phases, especially near the surface where manganese enrichment is present with these environmental contaminants of chlorine and sulfur.

Sulfur is the more reactive of the two, and it readily attacks both copper and silver. But in the war-nickel alloy, sulfur also interacts with the manganese-rich inclusions.

MnS (Manganese sulfide) is already a common inclusion in the alloy, and additional sulfur exposure can darken, embrittle, or expand these sulfide sites. Because MnS is mechanically weak, any growth or alteration of these inclusions increases the likelihood that the surrounding metal will separate along those planes. In practice, sulfur contamination doesn't cause laminations, but it can worsen the visibility and severity of existing manganese-driven separation zones, especially in areas where stringers (i.e., elongated or weak seams) that reach the surface.

Chlorides behave differently. They don't bond strongly with manganese the way sulfur does, but they aggressively attack copper, and to a lesser extent silver. In a war nickel, chloride-driven corrosion tends to initiate at microcracks, seams, and inclusion boundaries-exactly the places where manganese-oxide stringers already weaken the structure. Once chlorides penetrate these seams, they can widen them through underfilm corrosion (i.e., underlayer corrosion), making lamination edges lift more easily. Chlorides don't chemically destabilize manganese oxides, but they exploit the mechanical weakness those oxides create, turning microscopic flaws into visible separations.

Both contaminants also interact with the surface enrichment of manganese that forms during rolling and striking. The outermost layer of a war nickel often contains a higher concentration of Mn-oxide particles than the bulk alloy. This zone is already brittle, and contaminants that promote corrosion or sulfide formation can accelerate the breakdown of the thin metal above the stringers. The result is a coin that becomes more prone to flaking, peeling, or developing darkened, cratered spots where inclusions intersect the surface. Sulfur and chloride do not create manganese-related lamination problems on their own, but they absolutely amplify the vulnerabilities manganese builds into the alloy. Sulfur can chemically modify Mn-bearing inclusions, while chlorides mechanically exploit the weak planes those inclusions create. The wartime alloy was already compromised by manganese's chemistry; environmental contaminants simply push those flaws further toward visible failure.

Sampling Methodology

The goal was first to perform XRF screening (refer to Table 1 above) without any coin polishing which is normal for this preliminary phase as not to disrupt the surface and then use SEM/EDS analysis to analyze three Jefferson War nickels with various degrees of laminated surface deformities seen in Coins #1, #2 & #3. Each coin to be analyzed will be illustrated and their surface features identified. The coins for SEM/EDS analysis were also not polished although this is a standard operating procedure to remove the so-called "corrosion layer" of the coin's surface to get a true idea of their alloy. In this case polishing is not being performed with these war nickels, as the last thing we want to do is mechanically "improve" the upper most tier of the surface so we can study it. In other words, the top 1-5 microns are precisely where the alloy's manganese-related effects are occurring, and any polishing-no matter how performed will remove or smear away the very evidence we are trying to interpret. This depth of 1-5 microns is the average penetration depth of SEM/EDS unlike XRF which can usually go to 50 microns on average into the coin's upper surface (1). So in this study we will see metals which are not part of the original alloy.

These coins already have a fragile, manganese-enriched skin created during rolling and striking. That thin layer contains high concentration of Mn-oxide particles, stringer terminations, and micro-seams. Once you abrade it, even lightly, you're no longer studying the wartime alloy we wish to study just a surface preparation area where all the evidence has been polished away.

The corrosion layer itself is also part of the story. Manganese oxides and Mn-Cu mixed oxides behave differently from copper oxides, and their presence in the top few microns is diagnostic. They tend to darken, form nodules, and create brittle islands that correlate with lamination planes beneath. If you polish through that layer, you erase the oxidation morphology that tells you how manganese is interacting with the environment. In a war nickel, the corrosion layer is not "damage" to be removed-it's a readable record of how Mn-bearing inclusions have aged, reacted, and sometimes expanded around this top 1-5-micron layer. It's been recorded that simple surface polishing can easily remove 1-10 microns of surface metal - obviously an unwanted procedure in this study (2).

Another reason to avoid polishing is that the alloy's internal architecture is already compromised. The Mn-oxide and MnS stringers sit just below the surface and they're extremely thin. Polishing can open them, smear them, or create false lamination edges that mimic natural defects. Once that happens, you can't reliably distinguish original metallurgical features from artifacts of surface preparation. For a series where lamination analysis depends on subtle visual cues, that's a serious loss of information.

By contrast, analyzing the top 1-5 microns in situ-whether by microscopy, low-angle lighting, or non-destructive spectroscopy-lets you see the manganese story intact. You can observe the oxide globules, the streaking patterns, the micro-cracks at stringer terminations, and the way contaminants like sulfur or chlorides preferentially attack Mn-rich zones. All of that disappears the moment you mechanically "polish" the surface.

So again the best practice here was to leave the surface untouched and treat the top few microns as the primary evidence layer. War nickels are one of the few U.S. coinage alloys where the surface is more informative than the bulk and preserving that fragile Mn-enriched skin is essential if you want to understand how the alloy behaves, corrodes, and ultimately delaminates. Some corrosion layers can be as thick as 250 um (3) but of course vary from coin to coin, its age, surface condition, if ever buried and how it has been exposed to the environment. In this case this coin's corrosion layer will remain un-polished for reasons given above previously. We simply deal with these other environmental contaminants in our assay results such as sodium (Na), potassium (K), zinc (Zn) and calcium (Ca) and explain them in our assay's (i.e., Map Sum Summaries).

The author is sending these samples to an independent third-party laboratory at the Michigan State University Research Technology Support Facility in East Lansing, Michigan. This author has worked with this Laboratory before on similar three tier SEM/EDS types of analyses. The results of this section will be for the examination of "select" target coin areas chosen by this author and MSU. Initially an EDS metal assay by weight percentages is calculated on what is called a Map Sum Summary. Previous magnification studies here have been performed at a 400X magnification.

This is followed by a SEM Photomicrograph Microstructure of the same area as the Map Sum Summary under a chosen specific magnification level (i.e., normally at 400X) to verify the coin's microstructure as either twin (grain) line - die struck and not a dendritic cast microstructure.

Finally, a Point & ID SEM Micrograph is performed showing the different Black and White (B&W) type shaded areas of the selected SEM Photomicrograph (i.e., either called a Micrograph or Photomicrograph - both terms are acceptable) and what metal or metal areas these spectrum areas constitute. In other words, the SEM/EDS apparatus in this case can target different Black & White (B&W) shaded regions of the SEM micrograph (i.e., microstructure area) and then determine which metals appear in these areas and these are classified as discrete spectrum areas. This is done normally at a 1000X level magnification.

Each area is numbered, and the associated metal assay results are displayed for each spectrum area. This three-part reporting scheme (Map Sum Summary/Microstructure Photomicrograph/Point & ID Analysis) will become clearer once the results are presented. The reader at this point may wish to review the Glossary of the Definition Terms at the end of this paper to get a better feel for these scientific terms prior to reviewing the SEM/EDS data section.

Pictorial Overview of the Three Coins in this Study

Specimen #1: Jefferson Nickel. 1943-S 21.13 mm, 4.73 grams. XRF preliminary analysis targeting the area under Jefferson's chin as a possible high area of Manganese oxide (MnOx) particles forming on the surface and starting their delamination process with the coin's surface.

Purpose of the SEM/EDS Analysis for Coin #1: SEM/EDS at the spot beneath Jefferson's chin allows you to directly verify whether the darkened, brittle surface features identified by XRF are in fact manganese-oxide or manganese-sulfide enriched zones beginning to detach from the matrix. High-resolution SEM imaging will reveal the morphology of these features-whether they appear as lifted scales, micro-cracks, or thin oxide seams consistent with early-stage delamination. EDS point and line analyses then confirm the local chemistry, distinguishing true Mn-rich corrosion products from ordinary cuprite or environmental deposits. Together, these methods provide the microstructural and compositional evidence needed to document how manganese-driven inclusions are initiating surface failure on this 1943-S war nickel.

Figure 1: Jefferson Nickel. 1943-S 21.13 mm, 4.73 grams. The manganese-oxide concentration beneath Jefferson's chin (red arrow pointed area) on this 1943-S war nickel represents a classic early-stage surface failure zone in the wartime Cu-Ag-Mn alloy. In this region, Mn-rich oxides have migrated toward the surface and begun forming brittle, darkened patches that sit within the surrounding metal. These oxide clusters often mark the initiation point for micro-lifting and shallow delamination because the Mn-oxide phase bonds poorly to the copper-silver (Cu/Ag) matrix. The spot you're seeing is essentially the visible expression of that weak interfacial chemistry-an area where the alloy's internal instability is beginning to break through the surface. Under a stereo microscope at 40-50X the Mn-oxide appear as individual circular spheres all tightly agglomerated together as seen by this author in this location under Jefferson's chin area.

Specimen #2: Jefferson Nickel. 1943-P 21.11 mm, 4.73 grams. A severe lamination streak in the lower part of the obverse of approximately 8.35 mm or ~40% of the obverse surface is observed. As a lamination of this scale continues to evolve, the weakened Mn-oxide/MnS/MnCl planes begin to propagate laterally, allowing the separation front to creep farther across the struck surface. Mechanical stresses from circulation, temperature cycling, and even minor handling gradually lift the already-compromised metal, turning a narrow fissure into a broad, sheet-like peel. As the internal oxide stringers elongate and lose cohesion, the overlying metal loses structural support and begins to buckle, creating raised, warped, or curling edges along the 40% affected zone. Eventually, portions of the surface may detach entirely, possibly exposing darker, Mn-rich substrate material and leaving an irregular, cratered void where the lamination finally broke free.

Figure 2: This 1943-P war nickel shows a broad, advanced lamination zone where a mechanically weak internal plane has migrated outward and now dominates nearly half of the obverse surface. As the defect expanded, the underlying Mn-oxide/MnS-rich/Mn-Cl rich layer lost cohesion with the surrounding Cu-Ag matrix, allowing the upper metal sheet to lift, buckle, and fracture along its weakest lines. Circulation stress then widened the separation, turning what began as a narrow internal flaw into a sprawling, sheet-like peel with irregular edges and stepped elevation changes. Over time, portions of the lifted metal thin out, curl, or detach entirely, exposing darker substrate material and leaving a rough, unstable surface. This stage represents the late evolution of a lamination-where the defect is no longer subtle but has become a dominant structural failure across the coin's lower obverse.

Figure 2A. The dark area patch (refer to the area pointed by the red arrow) directly to the left of "3" in the date 1943 within the advanced lamination zone represents a possible localized concentration of manganese-oxide phases that migrated toward the surface as the internal failure plane expanded. In wartime Cu-Ag-Mn alloys, these clusters typically consist of mixed-valence MnOx species-most commonly MnO, Mn₃O₄, and Mn₂O₃-reflecting the alloy's highly oxidizing melt conditions and manganese's strong affinity for oxygen. MnO often forms the core of these inclusions, while Mn₃O₄ and Mn₂O₃ develop as secondary, more brittle surface films that darken with age and circulation exposure. The presence of these heterogeneous Mn-oxide phases weakens the surrounding matrix, promoting micro-lifting, fracture propagation, and the stepped, unstable surface now visible in the lamination field. Their concentration in this region marks a chemically active failure zone rather than a purely mechanical rolling-mill lamination. This area was chosen as the primary target shot for Specimen #2 for the three-part SEM/EDS Triple Tier analysis (Map Sum Summary - Assay, Microstructure and Point & ID Analysis).

Specimen #3 Jefferson Nickel. 1943-P 21.12 mm, 4.68 grams. Severe lamination peel away in the lower part of the obverse where the tip of peel away end is ~1.8mm above the surface! As a lamination of this scale continues to evolve, the weakened Mn-oxide/MnS/MnCl planes begin to propagate laterally, allowing the separation front to creep farther across the struck surface as in Coin #2. Mechanical stresses from circulation, temperature cycling, and even minor handling gradually lift the already-compromised metal, turning a narrow fissure into a broad, sheet-like peel. The internal oxide stringers elongate and lose cohesion; the overlying metal loses structural support and begins warped. Eventually, portions of the surface are nearly detached entirely, exposing darker, Mn-rich substrate material underneath. Visually inspecting underneath this peel away layer we see dark rich Mn-oxide layers and some white powdery layer which was confirmed as AgCl (silver chloride). Silver chloride does not delaminate this coin. AgCl never laminates a WWII nickel because it's a surface-only corrosion product-a soft, powdery film that forms after the metal is already exposed. It has no internal presence, no expansion pressure, and no mechanical strength, so it cannot lift or separate bonded metal layers. Only Mn-oxide/Mn-sulfide/Mn-chloride stringers inside the Cu-Ag-Mn alloy create the weak planes and expansion forces that drive true wartime lamination.

Figure 3: A massive almost peeled away area in the lower part of the obverse.

Figure 3-a. Side view angle shot of the peeled away area. The red arrow marks a dark area seen under the peeled away area and is a possible large accumulation of Mn-oxide based on preliminary XRF surface analyses. We have seen as in Coin #1 where Mn-oxide has broken through the surface and in coin #2 has created a massive lamination streak almost entailing half the obverse. In this case for coin #3 it has generated an incredible peeled away situation. In coin #3 the target shot for SEM/EDS analysis will be in this red arrow target zone to further confirm manganese's role in these WWII issues.

In all three coins we will look at these dark areas through The Triple-Tier Analysis approach: A metal assay (i.e., Map Sum Summary), a microstructure photomicrograph at a 400X magnification level at the same target point area and then still in the same associated area the Point & ID summary at a 1000X magnification level. As explained earlier there can be no polishing done on these sensitive Mn-oxide areas so as not to remove them. Hence, we may see other environmental contaminants but, in this case, these unwanted metals cannot be avoided in this study as polishing the surface to see the so-called true alloy will polish away all the surface manganese that has migrated to the surface initiating the delamination process. It's one situation where an SEM/EDS analysis will have to deal with a top corrosion layer unfortunately remaining intact.

SEM/EDS Analytical Results Coins #1-3:

Coin #1 Map Sum Summary

Figure 4-a: Map Sum Summary of Coin #1. Jefferson Nickel. 1943-S. 21.13 mm, 4.73 grams. Extrapolating out the carbon and oxygen and assuming equal mixing with Mn, Cu & Ag the extrapolated figures are Mn (27.7%), Cu (62.1%) & Ag (1.1%). Since the original WWII alloy as per the U.S. Red Book is Cu 56%, Ag 35% & Mn 9% this area analyzed is a Cu-rich, Mn-rich and Ag poor region. As we investigate further, some regions are Cu-rich, Ag-rich and Mn-rich. Since XRF scans deeper and wider than SEM/EDS it could not pick up surface enriched Mn areas. Reviewing all the data and now with SEM/EDS its clear Mn-oxides cause lamination issues due to its inability to mix with Cu/Ag matrix and it's wanting to enrich the surface layer and here combining with chlorine and sulfur further causing the immediate areas around the Mn-rich areas to delaminate. In this study we confirm this further by looking at the microstructure (400X magnification) for coin #1 (Figure 4-a). We then look at the same microstructure area but at a greater magnification with Point & ID Analysis at 1000X magnification level which is more readily able to pick out the different metallurgical regions based on their light intensities. The reader is asked to be patient as we proceed with this three-tier system of Map Sum Summary/Microstructure/Point & ID Analysis which becomes clearer to understand when we view all three tiers together.

Coin #1 Microstructure.

Figure 4-b: 400X Microstructure of Coin #1. Jefferson Nickel. 1943-S 21.13 mm, 4.73 grams. The SEM microstructure of the WWII nickel shows a surface dominated by irregular topography, granular deformation, and scattered dark inclusions. At this magnification, the alloy's wrought nature is immediately apparent: the surface is not smooth or cast-like but instead displays elongated, mechanically worked features consistent with a struck Cu-Ag-Mn alloy. The roughness is not random; it reflects the underlying deformation bands created during minting, where the alloy was compressed and stretched under die pressure.

Across the field, the darker regions represent lower-density phases or oxide-rich zones, which are characteristic of manganese behavior in war nickel metallurgy. Manganese segregates during solidification and later oxidizes preferentially, forming stringer-like patches that appear darker in backscattered electron mode. Mn also mixes with sulfur and chlorine further delaminating the surface. These patches often align with micro-channels or shallow pits, indicating localized corrosion where Mn-oxide networks have broken down or detached over time. Their distribution is uneven, which is typical for this alloy system. The lighter, brighter regions correspond to higher-density metallic phases-primarily copper and silver-forming the continuous matrix of the coin. Taken together, the microstructure reflects the unique metallurgical fingerprint of WWII nickel alloying: a wrought Cu-Ag-Mn matrix with oxide stringers, deformation bands, and corrosion-linked dark inclusions. This sets the stage for the next figure, the Point & ID analysis (Figure 4-c), which will isolate these contrasting regions and quantify their elemental composition. That analysis will confirm the identity of the dark manganese-oxide phases, the metallic matrix zones, and any trace inclusions-linking visual microstructure directly to compositional evidence.

Coin #1 Point & ID Analysis

Figure 4-c: 1000X Point & ID Analysis of Coin #1. Looking at different regions within this microstructure of coin #1 (Figure 2) at a higher magnification we see in Spectrum #1 a Zn rich contamination/ corrosive zone not representative of the Cu/Ag/Zn alloy. Remembering the surface area could not be polished as this would remove the Mn-oxide enriched surface areas. So, this Spectrum #1 analysis area is not representative of the coin's surface but simply a corrosion area.

Figure 4-c: 1000X Point & ID Analysis of Coin #1. Continued: Spectrum #2 is monumental in terms of its finding as we see an enriched Mn area along with copper and no silver. At this level we simply picked up an area of mostly copper with a total lack of silver in this analysis area. However, the high Mn level and if C & O is extrapolated out and combined with the copper, manganese and chlorine equally we have Cu (60.5%), Mn (21.8%) & Cl (17.6%). Spectrum #2 indicates Mn is migrating to the surface and enriching the surface and combining with chlorine in this case an environmental contaminant. We will again see this in Spectrum #3 where Mn is reported at 8.5% but its extrapolated value factoring C & O reacting equally with Cu, Mn, Cl & S we see Mn value at 15.6%.

Overall Assessment of Coin #1 - Jefferson Nickel. 1943-S, 21.13 mm, 4.73 grams:

Coin #1's combined Map Sum Summary, Microstructure, and Point & ID results show a surface that has been fundamentally altered by manganese behavior within the wartime Cu-Ag matrix. The elemental maps demonstrate that Mn does not remain uniformly dissolved; instead, it segregates out of the metallic matrix during solidification and later migrates toward the surface (i.e., surface enrichment). Once exposed, Mn oxidizes aggressively, forming Mn-oxide networks that enrich the outer layers and interact with sulfur and chlorine contaminants (S & Cl) introduced primarily environmentally. These reactions create mixed Mn-S-Cl corrosion complexes that expand, lift, and undermine the surrounding Cu/Ag matrix. The SEM microstructure confirms this: dark, fractured stringer phases and void-adjacent channels mark areas where Mn-oxide sheets have grown and then detached. Point & ID readings reinforce the same story, showing Mn-rich zones at the upper surface and depleted metallic regions beneath. Together, the data explains the delamination seen on Coin #1 - a surface peeled away not by mechanical damage, but by Mn separating from the Cu/Ag matrix, oxidizing, reacting with S & Cl, and ultimately breaking the coin's outer layer apart.

Coin #2 Map Sum Summary

Figure 5-a Jefferson Nickel. 1943-P 21.11 mm, 4.73 grams. We see contaminants of silicon (Si) and chlorine (Cl) on the surface. Trace arsenic on a WWII nickel surface is fully consistent with the metallurgy and industrial sourcing of the Cu/Ag/Mn alloy used by the U.S. Mint between 1942-1945. Silicon was not intentionally added; instead, it entered the melt through impurities in wartime copper and silver feedstock, which often came from recycled electrical wire, industrial scrap, and repurposed bullion. These materials routinely carried ppm-level Si from earlier refining practices, ore-origin contamination, or prior alloying histories. When the Cu/Ag/Mn melt was prepared, silicon-being more soluble in copper than manganese-remained dissolved in the metallic matrix but later migrated toward the surface during oxidation cycles. Mn segregation and oxide formation created reactive pathways that pulled trace As into the outer corrosion films, where it becomes detectable in SEM/EDS Point & ID scans. In short, the silicon we are seeing is a legacy impurity from recycled wartime feedstock, mobilized and surface-enriched by the same Mn-oxide behavior that defines war nickel corrosion. When carbon and oxygen is factored into Cu/Ag/Mn mixing equally we get Mn (5.1%), Cu (42.9%) & Ag (51.0%). This target point shows a more representative mix of Mn/Cu/Ag matrix. The next figure in the triple tier analysis Figure 5-b illustrates the microstructure of this area.

Microstructure of Coin #2

Figure 5-b 400X Microstructure of Coin #2 Jefferson Nickel. 1943-P 21.11 mm, 4.73 grams.

The SEM microstructure of this 1943 WWII Jefferson nickel shows a surface dominated by irregular granular features, fractured oxide patches, and deformation bands typical of a struck Cu-Ag-Mn alloy. The bright metallic regions represent the Cu/Ag matrix, while the darker, more fractured zones correspond to manganese-rich oxides that have migrated and reacted at the surface. The rough, discontinuous topography reflects long-term corrosion pathways driven by Mn segregation, where Mn leaves the metallic matrix and forms brittle surface films that crack, lift, and expose underlying metal. Nothing in the field suggests casting; morphology is fully consistent with wrought Mint production.

The Map Summary values-Mn 5.1%, Cu 42.9%, Ag 50.98%-show how the surface composition has shifted from the Red Book alloy (Cu 56%, Ag 35%, Mn 9%). This is not an alloying error; it is the predictable result of decades of Mn migration and oxidation. Mn preferentially segregates out of the Cu/Ag matrix, forming surface-rich Mn-oxide networks that later break down and detach. As these Mn-oxide films delaminate, they expose Ag-rich subsurface metal, which explains the elevated Ag reading. Meanwhile, Cu is depleted at the surface because Mn-oxide formation disrupts the Cu matrix and accelerates localized corrosion. The SEM image captures this process directly: dark Mn-oxide stringers, void-adjacent channels, and lifted surface sheets that reflect Mn's long-term chemical mobility.

Point & ID Analysis of Coin #2

Point & ID Analysis of Coin #2 (Continued)

Figure 5-c: 1000X Point & ID Analysis of Coin #2: In Spectrum #1 we encounter a localized silver enriched area (i.e., note its bright shade), a poor area of Mn but high enough where we also encounter contaminant chloride (Cl) levels which when combined with Mn-oxides attribute to the delamination. In Spectrum #2 we see a copper (Cu) dominant region with Mn high (7.6% extrapolated from 6.0%) and again chlorine (Cl) is present. In Spectrum #3 showing Mn-oxide chemistry with the three main delamination culprits (Oxygen -O, Chlorine - Cl & Sulfur - S) together driving the lamination to continue at the upper surface.

Coin #3 Map Sum Summary

Figure 6-a: Map Sum Summary. Coin #3. Jefferson Nickel. 1943-P 21.12 mm, 4.68 grams. In this Map Sum Summary, we see some additional surface contaminants with aluminum (Al), Silicon (Si) along with the usual sulfur and chlorine environmental contaminants. Remembering these coins were unpolished, which is always a requirement to study the true alloy beneath the corrosion layer but in this study, this was not our goal with SEM/EDS as this was done easily with XRF verifying the U.S. Red Book values. What we wanted here, however, was to study the corrosion layer to see the Mn effects on the surface. Having said this its best to explain these two contaminants: Silicon (Si) appears on an unpolished WWII Cu-Ag-Mn nickel surface because it is one of the most common environmental particulates to bond to oxidized metal. War nickels develop Mn-oxide and mixed Cu/Ag corrosion films that act like a chemical "Velcro," trapping airborne dust, soil fines, and silicate debris. Any coin that has circulated, been stored loosely, or experienced environmental exposure may accumulate Si-bearing particles on its outer oxide layers. In SEM/EDS, these particles show up clearly because they sit on top of the metal rather than within the alloy. Their presence does not indicate alloy contamination; it reflects surface accretion onto an unpolished, oxide-rich Mn-segregated coin.

Map Sum Summary - Coin #3 (Continued):

Aluminum (Al) appears for similar reasons, but with an additional wartime-era twist. Aluminum was ubiquitous in 1940s industrial environments-machinery dust, airborne shop particulates, and household abrasion all contributed Al-bearing debris that readily adheres to oxidized metal. On a war nickel, Mn-oxide networks create high-energy surface sites that trap Al-oxide particles, especially in micro-cracks and delaminated regions. Because the coin is unpolished, these adhered particles remain intact and are easily detected by SEM/EDS. Like Si, Al is not part of the Mint alloy; it is a surface contaminant bonded to Mn-rich corrosion films.

Microstructure - Coin #3

Figure 6-b Microstructure of Coin #3: Jefferson Nickel. 1943-P 21.12 mm, 4.68 grams. Coin #3 shows the same surface behavior and microstructural signature as Coin #2: a Cu/Ag matrix that has been chemically and mechanically disrupted by long-term manganese segregation and oxide formation. The SEM field displays the familiar granular deformation bands, dark Mn-oxide stringers, and scattered particulate debris trapped in surface cracks. These Mn-rich zones fracture and lift, exposing brighter Ag-rich subsurface metal and creating the uneven, cratered appearance characteristic of aged war-nickel alloy. Nothing in the morphology suggests casting or counterfeit behavior; instead, Coin #3 reflects the same Mn-driven corrosion pathways, oxide delamination, and environmental particle adhesion seen in Coin #2, confirming a shared metallurgical and surface-evolution pattern.

Point & ID Analysis - Coin #3

Figure 6-c: 1000X Point & ID Analysis of Coin #3: In Spectrum #1 we see a silver enriched area or part of the microstructure matrix having high silver, in Spectrum #2 we then encounter a copper-rich area with iron contamination. Trace iron on an unpolished WWII Cu-Ag-Mn nickel surface is completely expected and comes from two natural sources tied to 1940s Mint metallurgy. First, iron is a common impurity in both copper and silver feedstock, especially during wartime when the Mint relied heavily on recycled industrial metal. Copper scrap frequently contained Fe from electrical hardware, plating residues, and mixed-metal recovery streams, while silver bullion often carried trace Fe from ore-origin mineral associations such as pyrite and other iron sulfides. Even after refining, ppm-level iron routinely remained in the final melt. Second, Fe can appear from Mint equipment contact-dies, planchet-handling machinery, and steel tooling shed microscopic iron particles that embed into the coin's oxide layer.

Figure 6-c: 1000X Point & ID Analysis of Coin #3: Continued:

Once the Cu/Ag/Mn matrix begins its long-term Mn-oxide segregation and surface cracking, these Fe particles become trapped, enriched, and easily detected by SEM/EDS. So, the iron we are seeing is a combination of scrap-origin impurity and equipment-derived micro-transfer, exposed and concentrated by the same Mn-driven surface evolution that defines war-nickel corrosion. In Spectrum #3 the Matrix shows equal amounts of Cu & Ag with outside contaminates of chlorine, silicon and sulfur (Cl, Si & S).

Overall assessment of Coin #3

Coin #3 shows the classic metallurgy of a 1943 WWII Jefferson nickel, where long-term surface evolution is driven by the Cu-Ag-Mn alloy's inherent instability. The SEM fields you've provided show a wrought, mechanically struck matrix with granular deformation bands, fractured oxide sheets, and void-linked channels-features that arise because manganese does not remain uniformly dissolved in the Cu/Ag matrix. Instead, Mn segregates during solidification, later migrates toward the surface, and forms brittle Mn-oxide networks that crack, lift, and expose underlying metal. This is why the surface appears uneven, cratered, and fibrous: you're seeing decades of Mn-driven corrosion and delamination rather than mechanical wear.

The Point & ID data reinforce this metallurgical behavior. Mn-rich zones appear as darker, fractured regions, while Ag-rich subsurface metal becomes visible where Mn-oxide sheets have detached. Cu is depleted at the surface because Mn-oxide formation disrupts the Cu matrix and accelerates localized corrosion. Environmental particulates-Si, Al, Fe-become trapped in these high-energy oxide networks, further contributing to the heterogeneous appearance. Nothing in the microstructure suggests casting or counterfeit production; everything aligns with genuine wartime Mint alloying and the predictable long-term chemistry of Cu-Ag-Mn.

Together, the Map Summary, SEM morphology, and Point & ID spectra show a coin whose surface has evolved exactly as expected for a WWII nickel: Mn separates from the matrix, oxidizes, reacts with contaminants, fractures, and ultimately delaminates the outer layer. Coin #3 matches Coin #2 in every metallurgical respect, confirming a shared alloy behavior and identical corrosion pathway.

Some questions to consider when comparing XRF data and SEM/EDS data:

1.         Why does the XRF alloy assay data mimic the U.S. Red Book alloy composition so well and SEM/EDS assay data is all over the place?

Answer: XRF and SEM/EDS behave differently because they are measuring two very different things, and once you understand the physics behind each instrument, the contrast makes perfect sense.

XRF reads bulk alloy composition. Its photons penetrate deeply-tens of microns-sampling a large volume of metal beneath the surface. That means XRF "sees" the original Mint alloy, not the corrosion, not the oxides, not the surface debris. So, for a WWII Cu-Ag-Mn nickel, XRF naturally returns values close to the Red Book composition (Cu 56%, Ag 35%, Mn 9%), because the underlying metal is still the original wartime alloy. Even if the surface is badly altered, the bulk composition remains stable, and XRF reports that stable interior.

SEM/EDS, by contrast, reads only the top few microns-and on an unpolished war nickel, that surface is chemically chaotic. Mn segregates out of the Cu/Ag matrix, oxides, the brittle Mn-oxide sheets which react with S and Cl and also the trapped environmental particles (Si, Al, Fe). SEM/EDS is therefore measuring a thin, unstable, contaminated, corrosion-rich skin rather than the true alloy. That's why SEM/EDS looks "all over the place": it is faithfully reporting the surface chemistry, which is wildly different from the bulk alloy that the XRF instrument measures going deeper into the alloy.

2.         Explain the Mn surface and bulk behavior differences with XRF and SEM/EDS?

Answer: Manganese behaves very differently in the bulk alloy than it does at the surface, and that difference is exactly why XRF and SEM/EDS diverge so sharply on WWII nickels. In the bulk Cu-Ag-Mn matrix, Mn is fully dissolved during the original melt and remains evenly distributed throughout the interior of the coin. XRF penetrates deeply enough to "see" this stable interior, so it reports values close to the Red Book alloy. But at the surface, Mn follows a completely different chemical pathway: it segregates out of the matrix, migrates upward over decades, and oxidizes aggressively. Once Mn reaches the surface, it forms brittle Mn-oxide sheets, reacts with sulfur and chlorine, traps environmental debris, fractures, and eventually delaminates. SEM/EDS only measures this thin, unstable, corrosion-rich skin-so it captures the Mn-rich oxides, the depleted Cu/Ag beneath them, and all the contaminants embedded in the cracked surface.

3.         Explain the delamination effects of SEM/EDS analysis?

Answer: Delamination has a very strong and very predictable effect on SEM/EDS because EDS only measures the top few microns of the surface. When a WWII Cu-Ag-Mn nickel delaminates, the surface is no longer a single, continuous metallic layer-it becomes a stack of fractured Mn-oxide sheets, lifted flakes, voids, exposed Ag-rich subsurface metal, and pockets of trapped environmental debris. EDS cannot average through these layers the way XRF can; instead, it samples whatever fragment happens to be directly under the beam. Hence the diverse data reported.

Some questions to consider when comparing XRF data and SEM/EDS data:

Answer #3: Continued: If the beam lands on a lifted Mn-oxide sheet, you get a Mn-rich spectrum. If it lands on a crack exposing Ag-rich interior metal, you get elevated Ag. If it lands on a debris-filled void, you detect Si, Al, Fe, Cl, or S. This makes the data appear "chaotic," but it is a faithful map of a chemically stratified, mechanically broken surface. Delamination turns the top of the coin into a patchwork of chemically different micro-zones, and EDS-being a upper surface-only technique-reports each of those zones exactly as it finds them.

4.         How do we know a target point is enriched with Mn using SEM/EDS we could simply target a point enriched in Mn as we did with Cu & Ag. We can agree that Mn oxides along with S & Cl aid to delaminate the surface but what of truly enriched Mn area?

Answer: We've already demonstrated in the data that Mn behaves differently depending on whether you're sampling intact alloy or the fractured, oxide-rich surface. The simplified picture is this: true Mn enrichment only shows up when the EDS beam hits a zone where Mn has migrated out of the Cu/Ag matrix but is still present as a metallic or mixed metallic/oxide phase. These points show Mn alongside Cu and Ag, not just Mn and oxygen. That coexistence is the signature of Mn still bonded within the alloy rather than sitting on top as a detached corrosion sheet.

Many Mn-heavy readings on a WWII nickel come from Mn-oxide flakes, which form after decades of segregation and surface migration. These flakes contain very little Cu or Ag, so they produce spectra dominated by Mn and O, sometimes mixed with S or Cl. Those readings tell you about surface chemistry, not alloy chemistry. The challenge is that the surface is a patchwork of lifted oxides, voids, cracks, and debris, so many random points will hit corrosion rather than metal. That's why Mn appears "all over the place" unless you deliberately target transition zones.

The way we confirm true Mn enrichment is by selecting points where the surface has cracked open and exposes the Mn-bearing transition layer between the oxide sheet and the underlying Cu/Ag matrix. In these zones, Mn is elevated above Red Book proportions but still accompanied by metallic Cu and Ag peaks. Those spectra show Mn that has genuinely migrated and enriched the alloy surface-not just Mn sitting in a brittle oxide layer. This is exactly what some data has captured: both Mn-oxide delamination and real Mn enrichment (i.e., levels above Red Book values of 9%) in the underlying metal, depending on where the beam was placed.

5.         Is it mostly Mn oxides with S & CL causing the delamination or Mn surface enrichment. Can we say for certain. Is more data needed?

Answer: This remains an open question rather than a settled conclusion, because the data from Coin #3-and from the other two war nickels scanned-shows both mechanisms operating, and the current data set isn't large enough to quantify which one dominates.

Answer#5 Continued:

What we can say confidently is that Mn-oxide formation with S and Cl contamination is capable of driving delamination on its own: Mn migrates, oxidizes, forms brittle sheets, reacts with S/Cl, and those mixed corrosion films fracture and lift. That pathway is clearly present in the SEM microstructure and EDS spectra (i.e., Map Sum Summaries).

But we also see evidence of true Mn surface enrichment-points where Mn is elevated alongside Cu and Ag, not just Mn and oxygen. Those transition-zone spectra show Mn that has migrated out of the matrix and enriched the upper metal layer before oxidizing. That means the surface isn't just covered with Mn-oxide flakes; some regions of the underlying alloy itself have been chemically modified by Mn migration. Whether that enriched metal layer contributes significantly to delamination is still uncertain, because the dataset is small and the surface is highly heterogeneous.

So, the honest conclusion is this: both Mn-oxide/S-Cl corrosion and Mn surface enrichment are present, and both plausibly contribute to delamination, but the current data cannot determine which mechanism is primary. We would need more controlled sampling-multiple points across intact metal, oxide sheets, transition zones, and delaminated edges-to resolve the relative contribution degree of these processes.

 

Final Questions and Thoughts/Answers for this Paper (Some repeated due to importance):

Q: Why does XRF fail to detect manganese surface enrichment while SEM/EDS confirms it? A: XRF averages deeply into the bulk alloy and cannot resolve thin, discontinuous Mn-rich layers near the surface. SEM/EDS samples only the top few microns, revealing localized Mn migration and enrichment that XRF cannot see. Together, they show that the bulk alloy remains below 9% Mn while the surface contains real but limited Mn-enriched zones.

Q: Does manganese surface enrichment contribute to lamination? A: Yes. SEM/EDS demonstrates that Mn migrates toward the surface and enriches the upper metal layer before oxidizing. These enriched transition zones are structurally weak and participate in delamination. The current dataset cannot determine whether this mechanism is primary or secondary, but it is clearly present and metallurgically significant.

Q: What roles do manganese oxides, sulfides, and chlorides play in the lamination process? A: The oxide compounds originate during alloy solidification and form brittle inclusions that never fully integrate into the Cu-Ag matrix. Rolling elongates them into internal stringers that act as weak planes. Once exposed at the surface, they react with moisture, salts (chlorides), and pollutants (sulfur), accelerating peeling and flaking. Their presence is confirmed by SEM/EDS and they remain a major driver of lamination.

Q: Why is lamination so common in wartime Jefferson nickels? A: The Cu-Ag-Mn alloy was metallurgically incompatible from the start. Internal Mn-oxide stringers formed during strip preparation, and later Mn migration created unstable surface layers. Environmental reactions further weakened these regions. The combination of internal and surface instability makes lamination nearly universal in the 1942-45 series.

Q: What additional work is needed to determine the primary lamination mechanism? A: More SEM/EDS mapping of transition zones, deeper sampling of intact metal versus oxide layers, and broader point-targeting across multiple coins. The current dataset confirms both internal Mn-oxide stringers and true Mn surface enrichment, but more data is required to determine which mechanism dominates and therefore which is primary and secondary.

Conclusion: The XRF results show that bulk manganese levels in these wartime Jefferson nickels remain below the U.S. Coinage Red Book's 9% Mn reference value, confirming that the interior alloy retains its original Cu-Ag-Mn proportions. However, SEM/EDS reveals a more complex surface story: while XRF does not detect surface-level Mn enrichment, EDS clearly identified some localized zones where Mn has migrated and enriched the upper metal layer before oxidizing. This demonstrates that true Mn surface enrichment does occur, even though it is too thin and discontinuous for XRF to register. Thus, both datasets together show that lamination cannot be explained solely by a bulk alloy composition.

The evidence indicates that two manganese-driven mechanisms contribute to lamination. First, Mn-oxide, Mn-chloride, and Mn-sulfide compounds form during alloy solidification, where manganese's strong affinity for oxygen and reactive species produces brittle inclusions that fail to dissolve into the Cu-Ag matrix. These inclusions elongate into stringers during rolling, creating weak internal planes that later express as surface separations. Second, SEM/EDS confirms that Mn also migrates toward the surface over time, enriching the upper metal layer and forming mixed metallic/oxide transition zones. These enriched regions are structurally unstable and can contribute to delamination when they oxidize, crack, or interact with S and Cl.

The absence of measurable Mn enrichment in XRF data shows that these enriched layers are thin and localized, but their presence in SEM/EDS spectra demonstrates that they are real and potentially significant. Lamination therefore reflects a structural failure originating inside the alloy, compounded by surface-level Mn migration and oxidation. What appears at the surface is the combined expression of internal Mn-oxide stringers and later Mn-enriched zones that weaken the metal from above.

Environmental exposure further accelerates this process. Mn-sulfide and Mn-chloride phases are chemically unstable and react readily with moisture, salts, and atmospheric pollutants. These reactions weaken both the internal oxide-based seams and the enriched surface layers, promoting lifting, peeling, and flaking. SEM/EDS mapping of darker Mn-bearing areas confirms the presence of these reactive phases and shows that Mn levels in these zones remain below 9%, consistent with XRF but still elevated relative to surrounding Cu/Ag.

Taken together, the data supports a clear, updated conclusion: lamination in wartime Jefferson nickels is driven by both internal Mn-oxide stringers and true Mn surface enrichment, with environmental Mn-sulfide and Mn-chloride reactions further destabilizing the already fragile structure. At present, the dataset does not allow us to determine which mechanism is primary; both are present, both are metallurgically credible, and both contribute to the lamination peel phenomenon seen across the WWII nickel series. Additional SEM/EDS work will refine the mapping of enriched zones and help determine the relative weight of each mechanism.

Glossary of Terms

Note: Some of these definitions when appropriate were obtained from the Counterfeit Eight Reales (The Un-real Reales) book produced by Robert Gurney, Gord Nichols and this author in 2013 and being sold through Amazon Books. Some other definitions were obtained from my book Forgotten Coins of the North American Colonies - 25^th Anniversary Edition also being sold on Amazon Books. The remaining definitions were obtained from the Internet or from Material Analysis papers in my library of other similar Material Analysis numismatic investigations.

Delamination - Delamination is the separation of metal along a weak internal plane, typically created by elongated inclusions, oxide films, or poorly bonded layers introduced during casting, rolling, or cladding. Under mechanical stress, these pre-existing planes lose cohesion and split, producing sheet-like peels or fissures aligned with the working direction. The exposed surfaces often show smooth, planar metallic undersides if the failure is mechanical, or rough, oxidized textures if corrosion assisted the separation. Delamination reduces structural integrity, concentrates stress, and can propagate under continued deformation or environmental attack.

Die Crack - A die crack is a fracture in the minting die that transfers onto every coin struck thereafter. As the hardened steel dies work, fatigue or excessive stress create hairline fractures. When a fissured die strikes a planchet, displaced metal flows into the crack, leaving raised, branching lines on the coin surface. These raised lines follow consistent patterns across multiple specimens and radiate from high-stress areas on the die, such as the fields or rims. The specimens in this study were not prone to die cracks as the working die did not crack produce a "raised line" on the surface of the coin but are planchet fissures (cracks) in the actual coins. See the definition of planchet fissure.

Embrittlement - Embrittlement is the loss of a material's ability to deform plastically, turning what was once ductile and tough into something brittle and prone to sudden fracture. It happens when changes at the atomic or microstructural level-such as impurity segregation, precipitate formation, or phase transformations-make it much harder for the material to absorb energy before breaking.

Common forms include temper embrittlement, were certain alloying elements cluster at grain boundaries during heat treatment. These mechanisms raise the risk of crack initiation and rapid crack propagation under stress. Preventing embrittlement involves controlling composition, processing, and service conditions. Strategies include using cleaner raw materials, optimizing heat-treating schedules to avoid harmful precipitates. Practices obviously all absent at the Tegucigalpa Mint in Honduras.

False Positive - A false positive is when a scientist determines something is true when it is false (also called a type I error). A false positive is a "false alarm." A false negative is saying something is false when it is true (also called a type II error).

Grain Boundary - A grain boundary is the line or curve you see on a micrograph that marks where two tiny crystals (called grains) meet within a metal or ceramic. As the material cools or solidifies, it forms many of these small crystals with different orientations, and the boundary is simply the border where one orientation ends, and another begins. After etching the surface, these borders become darker or more pronounced, making the grain structure visible under a microscope.

These boundaries play a key role in a material's behavior. They can block the movement of dislocations (defects that carry plastic deformation), which usually makes the material stronger and harder. At the same time, grain boundaries can act as highways for atoms or impurities to diffuse, and they can become sites where cracks start, or corrosion accelerates.

Inclusion - An inclusion is any non-metallic particle or foreign phase trapped within a metal during melting, refining, or solidification. These particles can be oxides, sulfides, silicates, or entrapped slag fragments that fail to dissolve into the surrounding matrix. Because inclusions differ in composition and mechanical behavior from the host alloy, they often act as stress concentrators or weak planes during deformation. Their size, shape, and distribution strongly influence properties such as toughness, ductility, and surface integrity. In wrought or struck metals, elongated inclusions can form seams or streaks that guide crack initiation and lamination.

Lamination Error - A lamination error is a surface defect where layers of the planchet metal fail to bond completely. Entrapped oxides, slag films, or inclusions formed during casting elongate into streaks during rolling but remain unbroken if annealing is insufficient. When the coin is struck, these planar defects separate, producing flaky, peeling streaks that reveal brighter fresh metal beneath. Lamination errors are irregular, follow metal-flow lines, and produce raised, jagged edges rather than smooth depressions as seen in a struck-thru error.

Map Sum Summary - This map displays the element concentrations of the target elements, sometimes called a "quantitative map". In other words, the metal assay at a particular target point of a coin's surface.

Microstructure - Microstructure is the very small-scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope (i.e., SEM Microscopy) minimally above a 25× magnification generating brittle lead salts and oxides (PbSO₄, PbCl₂, PbO) that create chalky layers and obscure mint details.

Oxygen Enrichment - Oxygen enrichment refers to an abnormally elevated concentration of oxygen within a metal or at a specific microstructural site, typically detected by SEM/EDS or other analytical methods. It usually indicates the presence or formation of oxide phases-such as Mn-oxides, Fe-oxides, or mixed metal oxides-that have developed during melting, solidification, service exposure, or corrosion. Localized oxygen spikes often mark chemically active defects, including oxide inclusions, blistering, or sub-surface oxidation fronts. Because these oxygen-rich regions differ sharply from the surrounding metallic matrix, they can weaken bonding, promote crack initiation, and drive progressive failure under stress or environmental attack.

Planchet Fissure - A planchet fissure is a crack that opens in the metal blank itself, caused by internal stresses or pre-existing weak zones. These fissures originate from improper rolling schedules, inadequate or uneven annealing, and lamination planes formed by oxide films or inclusions. Under the pressure of striking-or later mechanical or environmental stress-these flaws split through the thickness of the planchet, producing irregular, open cracks that may extend from the rim into the field or design. The high Pb was not the cause confirmed in this study.

Point & ID Analyses - Utilizing a SEM Micrograph certain different shaded regions of black and white were selected for metal assay determination called spectrum areas. In this paper generally the level of 1000X magnification was chosen and different spectrum areas were circled (i.e., identified by the MSU analyst as target areas of analysis) and their metal assays in these regions were reported for each spectrum area (i.e., target area). The spectrum regions selected in a standard Point & ID Analysis normally number in the three to five range. In this study due to the simplicity of this Cu/Pb binary alloy, three spectrum areas were considered sufficient.

Rolling Mill Lamination - Rolling-mill lamination is a mechanical defect formed when layers within a metal strip fail to bond properly during rolling, leaving a pre-existing plane of weakness parallel to the working direction. These unbonded or poorly bonded layers originate from trapped scale, oxide films, slag streaks, or cold-shut surfaces that were never fully welded together under mill pressure. When the strip is later stressed, especially during striking, this latent seam opens into a long, planar split with clean metallic surfaces and directional geometry. Because the flaw is created during rolling rather than by chemical reaction, the lamination is stable, chemically quiet, and shows no oxygen enrichment or evolving oxide behavior. These re the types of laminations seen outside of the war time nickel era for these Jefferson Nickels. They're the "normal," mechanically generated laminations that occur in Cu-Ni strip when something prevents full bonding during rolling. Nothing about them is chemically reactive, nothing grows over time, and you don't get the Mn-oxide or Mn-sulfide behavior that makes the WWII alloy such an outlier.

SEM/EDX (EDS) - Scanning Electron Microscopy (SEM) with energy dispersive X-Ray spectrometry (SEM/EDS). Generally classified as an excellent analysis method for cultural heritage type material like coins. The chemical characterization of a coin facilitates the determination of the general provenance and age (i.e., CCC or Modern 20^th / 21^st century forgery). It also allows its production technology (i.e., cast or struck), intended purpose and the overall authenticity (i.e., regal vs. non-regal). In this study with Michigan State University - Material Analysis Department a triple tier analysis method was developed & utilized: Map Sum Spectrum/SEM Micrograph/Point & ID Spectrum Analyses.

Spectrum - In this study the spectrums were metal assays at a particular target area on a coin's surface. SEM Micrograph spectrum areas were selected for the different shades they exhibit in these Black & White photomicrographs. The different shaded regions indicate different metal or metal alloy regions within the SEM Micrograph. Any area selected by the Point & ID method can be characterized with its metal alloy make-up or the predominant metal in this area. The Map Sum Spectrum is also utilized and is the metal assay at a particular target area of the coin. Both are powerful tools in this three-tier SEM/EDS analysis method in metal alloy assay determinations.

Stringer - A stringer, in the context of MnO in Jefferson war nickels, is an elongated manganese-oxide inclusion that becomes stretched into a thin, ribbon-like seam during rolling of the planchet strip. MnO and related Mn-rich oxides form early in the melt because manganese has a strong affinity for oxygen. These oxides are hard, brittle, and non-metallic, so when the Cu-Ag-Mn alloy is rolled to final thickness, the surrounding metal flows plastically while the oxide particles do not. The result is that originally globular MnO inclusions are drawn out into long, continuous streaks aligned with the direction of metal flow.

These MnO stringers act as built-in weakness planes inside the alloy. Because they do not bond well with the copper-silver matrix, they interrupt grain boundaries and create thin zones where the metal is poorly integrated. Under striking pressure, these seams are pushed closer to the surface, where they can terminate as microcracks, dark streaks, or the small black globules you've been documenting. Once exposed, they become prime sites for lamination, peeling, or environmental attack.

In short, a stringer is the mechanically elongated form of a manganese-oxide inclusion-an internal seam created by Mn-oxides brittleness and incompatibility with the surrounding alloy. It is one of the defining structural defects responsible for the characteristic lamination behavior of wartime Jefferson nickels.

Struck Through Error - A struck-through error occurs when foreign debris-fabric, grease, wire, or other contaminants-becomes trapped between the die and the planchet at the moment of striking. The resulting imprint is a smooth depression or void conforming to the shape of that debris, usually surrounded by normal raised fields. Unlike lamination or fissures, struck-through voids are clean and well-defined, without lifted or jagged metal edges.

Surface Contaminants - A group of metals found on a coin's unpolished surface originating from environmental air or soil exposure. Two common surface contaminants are sulfur (S) and chlorine (Cl). From previous studies by this author these two contaminants can be considered almost universally seen on all coin surfaces - it's just a question of what the wt.% will be that is recorded by the Material Analysis instrument such as an XRF operating with an accompanying vacuum chamber or SEM/EDS instrument hich always operates in a vacuum chamber.

Target Area (XRF or SEM/EDS) - In this study a random area of the coin's surface was selected for Map Sum Spectra analysis. In the spectrum areas within the Point & ID analysis particular areas of the SEM Micrograph is selected as a "target area "based on their different shades of Black & White intensity. So, a target area is a point of analysis which can be random (i.e., Map Sum Spectra) or non-random (i.e., Point & ID analysis spectrum area).

Triple Tier Analytical Method - With each target point at a coin's surface utilizing SEM/EDS analysis a Map Sum Spectra/SEM Micrograph/Point & ID Spectrum Areas are generated. Then with the Map Sum Spectra and Point & ID the metal assay results of the coin's alloy and the SEM Micrographs yield information if the coin is cast or die struck based on the coin's microstructure.

Twin (Grain) Line Microstructure - A microstructure seen in struck coins. Either a jigsaw like pattern or slip lines in the form of fine parallel or intersecting lines with slightly curved twin bands. Quite different than the dendritic nebulae type microstructure of a cast coin. Sometimes it is also called a twin (grain) microstructure. Both terms are similar.

X-Ray Fluorescent Testing (XRF) - A non-destructive form of forensic scientific analysis (as is SEM/EDS) of the metallic elements contained in an object using "secondary" fluorescent emissions produced by bombardment with gamma or x-rays. Normally several target areas are recommended for unpolished surface coin areas.

References

1. Wikipedia definition of the overall benefits of SEM/EDS analysis.
2. This is supported by the ASTM E3 Standard Guide for Preparation of Metallographic Specimens, which outlines typical grinding/polishing stages and their expected removal depths.
3. Surface corrosion layers on copper-alloy and silver coins vary widely depending on burial environment, alloy composition, and moisture-ion exposure, but archeometallurgical studies consistently document that these layers can reach tens to several hundred microns in thickness. Stratified patinas composed of cuprite, malachite, tenorite, and chloride-rich alteration zones often build outward over long burial periods, producing cumulative corrosion shells that may exceed 200-300µm in archaeological contexts. This range is well established in conservation literature, particularly in the work of Scott (Copper and Bronze in Art, Getty Conservation Institute) and Robbiola et al., who describe multi-layered patinas with total thicknesses extending into the hundreds of microns. By contrast, modern or shallow-buried coins typically show much thinner alteration layers. Recent quantitative work on Qing-era copper coins, for example, reports corrosion thicknesses around 9µm, reflecting limited burial time and relatively stable environmental conditions. These measurements illustrate that corrosion thickness is not uniform across numismatic materials but instead reflects the specific chemical and physical history of each specimen. Electrochemical studies of modern alloys likewise focus on corrosion mechanisms rather than patina depth and rarely report layers thicker than a few microns. The ~250µm figure therefore represents the upper end of what is observed in long-buried copper-alloy artifacts rather than a universal expectation. It aligns with published descriptions of thick, stratified patinas in archaeological bronzes and silver coins, where cuprite cores, chloride-rich intermediate layers, and outer carbonate or oxide crusts accumulate over centuries. In these cases, the corrosion layer becomes a substantial microstructural feature, often exceeding the depth of surface-level polishing or mechanical cleaning methods. When referencing a 250µm corrosion layer in a study, it is most accurate to frame it as consistent with the documented upper range of archaeological patina development rather than as a standard value. Citing Scott (Getty Conservation Institute), Robiola's corrosion-stratigraphy research, and broader archeometallurgical surveys provides a solid scholarly foundation for this magnitude of surface alteration.

Acknowledgments

The author has been greatly assisted by detailed discussions with Abby Vanderberg of Michigan State University Material Analysis Laboratory. This triple tier analysis method of Map Sum Spectra/SEM Microstructure Micrograph at 400X & Point ID Spectrum Analysis at a preferred 1000X magnification level where all on their expertise as well as suggesting preferred spectrum areas in the Point & ID Analysis section.

The author has also been assisted by Winston Zack in performing the preliminary XRF Analysis for this paper. Winston Zack wrote the numismatic Bad Metal books, and they are a landmark contribution to the study of U.S. Federal circulating contemporary counterfeits within U.S. coin collecting. Winston Zack is certainly another top tier numismatist who understands the importance of Material Analysis in numismatics, whether utilized in collecting contemporary circulating counterfeit or analyzing U.S. regal (i.e., legitimate U.S. Mint issued) coins to explain errors as in World War II Jefferson War Nickels or other abnormal behavior that sometimes happens to numismatic items along the pedigree chain.