DALLAS, TX.- Collectors will have the opportunity in January to acquire the discovery example of one of the most important U.S. modern errors. Heritage Auctions will be offering the only confirmed 2014 $50 Gold Eagle incorrectly struck on a .9999 American Buffalo Planchet at the 2017 Florida United Numismatists Auction, January 4-9 in Fort Lauderdale, Fla. As uncommon as it is stunning, the type is the only wrong planchet error known in the entirety of United States gold coinage history.

"Wrong planchet errors are virtually unknown in the U.S. gold series," Heritage Auctions President Greg Rohan said. "There have been exceedingly rare instances of non-gold coins struck on gold planchets, but this is the only certified U.S. gold issue struck on an incorrect gold blank."

Though the Gold Eagle and American Buffalo $50 coins have the same 32.7-milimeter diameter, they differ in thickness and weight. Due to the American Buffalo's finer composition, it is thicker and lighter.

The coin is graded MS69 by PCGS and is the only confirmed example of the error. One other is thought to exist, but it is not yet certified. APMEX officials discovered the error and conducted non-destructive fineness tests before sending it to NGC for authentication and grading. NGC graded the coin MS69 with a regular strike designation. Officials then submitted the coin to PCGS, where the wrong planchet error was certified.

Like all U.S. gold bullion coins, the error was struck at the West Point Mint. The mint has not commented on how the wrong blank was used, or how many could have been struck.

Coin World magazine quoted dealer Fred Weinbergabout a similar modern silver error: "A 1998 American Eagle silver dollar graded and encapsulated PCGS MS68 in 2013, struck at the San Francisco Mint on a 38.1-millimeter .900 fine silver dollar commemorative coin planchet instead of the intended American Eagle 40.6-millimeter .999 fine silver planchet, subsequently traded hands privately for in excess of $50,000."

Of similar rarity, the Gold Eagle is potentially more desirable and could bring bids at that level or higher among error collectors and modern gold specialists.

Heritage Auctions' FUN Auctions will be held Jan. 4-9, with its Platinum Night Auction taking place Jan. 5.