Although there are a few known Proof Eisenhower Dollar mated pairs, these have been off-metals that were struck at the same time in the collar. An example would be a Proof Ike Dollar struck on a Cent that was mated to a Proof Ike Dollar struck on a Dime.
This unique Proof Eisenhower Dollar mated pair is the first known of this type of error. 1973-S Proof Eisenhower Dollars were only struck in clad, composed of 75% copper and 25% nickel, over a pure copper center. It appears that this mated pair was intentionally produced, only because they are Proof Ike Dollars and given the fact that both of these were kept intact together, recently surfacing after 50 years.
There are a few known U.S. coins that were struck on silver or clad layers but these are in lower denominations and struck by circulation dies. Although the type of error is not unique, the circumstances point to this proof mated pair as being intentionally struck.
A silver Dollar layer was placed on top of the clad Dollar planchet and were struck simultaneously. They match 100% and both have a very high rim and lock into place when the silver layer is placed on top of the clad Ike Dollar.
In actuality, this is an off-metal Proof Eisenhower Dollar (on a silver layer) mated to a regular issue clad Proof Eisenhower Dollar. It is unique in several ways and to date, has no equals.
Exotic and Intentional U.S. Error Coins In The Marketplace
One of the most controversial categories of U.S. coins are mint errors. Many dealers and collectors, as well as coin auction houses, buy, sell, trade and auction many rare, exotic and unique major mint errors. Obviously, some of these defy logic and were intentionally created and taken out of the Mint.
In the early 2000's, a group of several hundred U.S. error coins were found in a safe-deposit box. Fred Weinberg purchased this group which included coins struck for proof sets and also coins struck for circulation. This group was auctioned by the California State Controller's Office of Unclaimed Property. The U.S. Secret Service inspected and released this collection to the State of California determining that it was legal to own. The State of California then auctioned the collection and the rest is history.
Another example of U.S. error coins escaping the Mint occurred in the 1970's. A hoard of proof error coins were smuggled out of the San Francisco Mint inside the oil pans of forklifts that were being serviced outside of the Mint. This topic was discussed in the June 6, 2022 Issue of Coin World, which covered Fred Weinberg's account of this story. The Coin World Managing Editor concluded:
Obviously, the marketplace accepts these coins, and some collectors are happy paying thousands of dollars for coins that show every indication of having been created through illegal means.
In Episode 11 of the PCGS video series Slab Lab, Seth Chandler interviews Fred Weinberg. In part 2 of the interview, Fred explains in detail why mint errors that are decades old are not recovered by the U.S. Mint. Fred's recollection of conversations in his office with the Chief of the U.S. Mint Police are extremely insightful and explain why the Mint doesn't attempt to recover error coins from decades ago.
Mated Pairs are featured in the NLG award
winning book, World's Greatest Mint Errors.