Your weird looking coins might be error coins! Here's how to tell what's a legit error coin from the U.S. Mint (like the rare 1990 penny, valuable doubled die coins, and bubbled coins) and what's an altered coins or novelty coin (like two-headed coins, colorized coins, gold-plated coins, really small coins, really large coins, coins with odd rims and edges, dimes & quarters without edge grooves). Plus a list of some of the most common U.S. coin errors that you could actually find in your pocket change!