Air-space-cyber Power Maintenance Coin. Challenge Coins are a tradition that started during WW 1. The first coins were issued to battalions as symbols of camaraderie and unity, and have been prized by Veteran’s ever since. Over time the “challenge” came when the service member having a coin to show proof of membership in a campaign, battle group or event. Challenge Coins are often traded between service members and are a great source of pride.