There is much debate on when and where the Challenge Coin made its appearance. The most widely accepted origin story comes from a crowded bar during the Vietnam War. With limited space and alcohol, the owner wanted to ensure that the patrons being served had actually been in combat. Soldiers began carrying brass coins with their unit insignia engraved as proof of their exploits. The practice was called a "coin check" by the barkeep, thus the Challenge Coin was born. Challenge Coins became a tradable item gifted to another person as a sign of deep respect.