Error Coins
Mint-made errors are errors in a coin made by the mint during the minting
process. Mint error coins can be the result of deterioration of the minting
equipment, accidents or malfunctions during the minting process, or
intentional interventions by mint personnel. Accidental error coins are
perhaps the most numerous and in modern minting are usually very rare,
making them quite valuable to numismatists.

Misprint Error Coins

Amazon Collectible Coins