The recent Heritage Auctions coin sale at the FUN convention in Tampa (January 6-11) included a numismatic rarity - a Roosevelt Dime struck on a zinc-coated sixpenny nail.

Little is known of how or when the nail found its way onto the coin production line, but the image of Roosevelt struck onto the flattened nail was enough to earn it a grading of MS65 PCGS.

Roosevelt dimes have been in circulation since 1946

Described as one of the most unusual pieces to ever come out of a United States Mint, the nail was expected to sell for around $10,000, but achieved a final price of $42,300.

The anonymous buyer is believed to be a US collector whose rarities span a range of collecting categories.

"Significant error coins are among the most sought-after in the hobby, as evidenced by the spirited bidding among collectors over this coin," said Greg Rohan, president of Heritage Auctions.

"This is certainly among the most unique and mysterious errors to ever come to auction. The truth is, no one really knows how or why it was struck."

The auction in Florida also included another notable coin error in the shape of a 1943-S Lincoln 1C piece struck on a bronze planchet.

During WWII, the US government changed the composition of the penny from bronze to steel, to save copper for the war effort. However, a handful of 1943 Lincoln cents were mistakenly struck in bronze rather than steel, and today are sought-after by collectors.

Just six confirmed 1943 bronze cents are known to exist, and the example offered at Heritage, graded AU55 PCGS Secure, sold for $211,500.

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