This installment in the series covers mint errors that can
occur when something goes wrong with a coin's planchet.
Every year, mints for major countries produce billions of coins. Despite sophisticated technology and comprehensive quality control efforts, some mistakes are made. Coins with mistakes are called "mint errors" and are among the most popular segments of numismatics.
Coins are created when a pair of dies strike a planchet, imparting the design. But sometimes a wrong or faulty planchet is used. Here are some examples:
Wrong planchet: This error occurs when a correctly made planchet from one denomination is accidentally fed into a press striking another denomination. Examples are a nickel struck on a cent planchet and a cent struck on a dime planchet. The coin struck on an incorrect blank will weigh exactly what the denomination of that blank would have been. An even more dramatic wrong planchet error is a coin struck on a previously struck coin.
A coin struck on the wrong planchet.
Transitional error: This occurs when a coin is struck on a planchet from a previous year with different metal composition. The most famous is the 1943 Lincoln Cent struck on a 1942 copper blank. Other famous examples include 1965 US coinage struck in silver instead of clad. There are also transitional errors struck on blanks intended for the next year. An example is 1964 coinage in clad instead of silver. More recently, transitional errors were discovered involving the Susan B. Anthony and Sacagawea Dollars of 1999 and 2000.
All 1943 Lincoln Cents were supposed to be struck on steel planchets, and all 1944 Lincoln Cents were supposed to have returned to the traditional copper planchets. Here are examples of transitional errors with the wrong-metal planchets.
Clipped planchet: Planchets are punched from large sheets of metal. After blanks are cut from a sheet, it is moved forward before more blanks are punched out. If the sheet fails to be fed far enough ahead, the punch will overlap an already punched area, causing that planchet to have a circular "clip" of missing metal. A good way to tell if the coin is an error or simply damage that occurred outside of the mint is to look for signs of metal flow into the blank area, which indicates a genuine clip. The types include curved, straight and ragged edge.
A coin with a clipped planchet.
Struck fragment: The blanking press takes the coils of metal strips and punches blanks out of it, ejecting the webbing at the other end. The webbing is cut into small scrap pieces to be melted and recycled. Occasionally, a scrap piece will be mixed with the blank planchets and struck by the dies. Struck fragments are rare in the larger denominations. These can be uniface or struck on both sides.
An example of a struck fragment.
Lamination: Dirt and impurities in the metal of the planchet can manifest themselves as cracks and peels on the struck coin. A planchet can split if impurities are severe enough.
A coin with a cracked planchet.
Missing clad layer: This error happens either when a clad layer was missing before the strike or when the layer was loose and separated from the rest of the coin after the strike. The side of the coin with the clad layer missing will be copper-colored, showing the exposed core of the coin.
1970-D Quarter graded NGC Mint Error MS 64 - Missing Clad Layer on Reverse.
Misplaced or missing center hole: Some country's coins feature holes at the center of their planchets. Occasionally, these holes will be misplaced or missing altogether.
1995M Spain Castilla & Leon 25 Pesetas, Off-Set Center Hole, NGC MS65
Missing edge lettering: This mint error has been discovered in the US Presidential Dollar series. Some of these coins inadvertently left the United States Mint without edge-lettering on them. The inscriptions "In God We Trust," "E Pluribus Unum," as well as the mintmark and year are absent from these coins.