The challenge coin game is a military tradition with murky roots. The game is played where one service member at a bar challenges another to present their challenge coin. If the challenged doesn't have their coin, they have to buy the challenger a drink. If the challenged service member has their coin, they get a round on the challenger.
Few people play the game anymore, but unit coin designs say a lot about a command. Here are some of the best challenge coin designs we've seen.
1. U.S. Army diver coin
Photo: Cristina Collesano
It's hard to tell from the photo, but this coin is clear. It's a rare choice that makes it stand out despite a relatively simple design.