1968-S Kennedy Half Dollar
Struck on 125 grain (8.1 gram) Magnetic Planchet
PCGS Proof 62
Piece de Caprice
Ex Fred Weinberg Collection
UNIQUE
$25,000

There are many major mint errors known on U.S. proof coins including off-centers, off-metals, double and multiple strikes, bonded coins, and mated coins, but this is the only one known struck on a magnetic planchet.

Over my 45 years dealing in major mint errors, I've never encountered another U.S. proof mint error struck on a magnetic planchet. Fred Weinberg, who had this in his personal collection for decades, sold it in 2024. He stated that "as far as I know, this is the only known U.S. proof mint error on a magnetic planchet and it is fascinating!"

The pressure of the Kennedy Half proof dies expanded the diameter of the 8.1 gram magnetic planchet to the diameter of a regular Kennedy Half Dollar.

Although authenticated and certified by PCGS as Proof 62, it is as struck. The magnetic planchet does not have the reflectivity of a regular polished proof planchet, nor does the cameo portrait show on the obverse. It has the typical look and color of the few mint state U.S. coins that are known to be struck on smaller magnetic washers.

It is amazing that this unique proof rarity survived over a half-century. Obviously this was an intentionally produced proof mint error (piece de caprice). This spectacular and enigmatic proof Kennedy Half Dollar struck on a magnetic planchet is in a class by itself.

Intentional Errors 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.

Off-Metal Errors are featured in my NLG Award winning book,
World's Greatest Mint Errors.