Our most popular and economical collector's coins, these 3" zinc challenge coins rival the quality of our brass coins at a lighter weight. Challenge coins originated during World War I and were issued to battalions as symbols of camaraderie and unity. Later, they were used as a way of verifying membership in clubs, groups and military units. They are now commonly given away at military and DOD meetings as a token of appreciation. Add a customized imprint of your choosing to create a cherished keepsake