These 2.25" zinc challenge coins rival in quality to our brass coins at a lighter weight and are bound to make outstanding collector's items! Originating during World War I, Challenge coins were issued to battalions as symbols of camaraderie and unity, and 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 memento by adding a customized imprint of your choosing.