Certain rare Lincoln pennies have sold for tens of thousands of dollars — and a few may still be circulating today.

One of the most famous examples is the 1943 bronze Lincoln penny. During World War II, the U.S. Mint switched from copper pennies to steel pennies in order to save copper for wartime manufacturing. However, a small number of bronze blanks from the previous year were accidentally used to strike a few 1943 pennies.

Because of this mistake, the rare bronze 1943 penny became one of the most valuable coins in American history.

Some collectors have paid up to $85,000 or more for a genuine example depending on its condition.

There’s a simple way to check if your 1943 penny could be valuable. Most 1943 pennies were made of steel and will stick to a magnet. The rare bronze versions will not stick to a magnet.

If you ever find a 1943 penny that doesn’t stick, experts recommend having it evaluated by a professional coin dealer.

That small piece of change could be worth far more than you think.