PHILADELPHIA (CNN) –– They say a penny saved is a penny earned, but this particular one could net you $85,000.

Copper pennies from 1943 are among the most valuable coins out there since America was in the midst of World War II and conserved copper strictly for the war effort.

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All pennies were cast in stainless steel that year, but some copper versions managed to sneak through by mistake. One of these pennies reportedly sold at auction in 2010 for $1.7 million. Appraisers estimate that a 1943 copper penny in average condition would bring in $60,000 at auction while mint condition would garner $85,000.

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If you come across any pennies dated 1943, they’re already rare for being made of stainless steel, but use a magnet to check. If there’s no magnetic pull, it’s likely copper!

The U.S. Mint returned to copper pennies after the war since the steel pennies rusted quickly and were easily confused for dimes. In 1982, rising copper prices forced another penny overhaul with a switch to mostly zinc coins covered with a copper veneer.

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