In the market for a collector's item that rivals the quality of our brass coins at a lighter weight? Look no further than these 2.75" zinc Challenge coins! 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. Create a cherished keepsake by adding a customized imprint of your choosing.