There's a marketplace for coin enthusiasts to buy and sell rare coins, where you could make some decent money if you find one ...

This rare coin is missing its "D" mint mark, and other varieties have noticeable but weak mint marks. The “no D” variety is by far the most valuable and has no trace of the mint mark whatsoever.

This rare coin is notable because it doesn’t contain a mint mark; the U.S. Mint deliberately didn’t include mint marks on coins produced from 1965 to 1967, to limit coin hoarding.

THREE sisters finally sold a rare coin with a missing mint for a whopping $500,000 ... It's extraordinarily rare because it makes up just one of two known coins to exist without an S mint mark ...

Some of the rarest and most valuable coins in U.S. history owe their worth to minting errors that slipped through unnoticed. Coins like the 1943 Copper Penny, struck in copper instead of wartime ...

1922 No D: The Denver Mint was the only one to produce pennies this year, but some were mistakenly minted without the “D” mint mark. Collectors highly seek after these.

Ranging from $500 in average condition to $3,200 in mint state, the 1877 Indian Head Penny is without a shadow of a doubt one to keep in your collection. Are there any coins you can think of that ...

Some mint marks are scarcer than others, like the S in this coin’s case, meaning that 1943-S steel pennies are often the most valuable (not including coins with rare errors). Mint Errors ...