A challenge coin is a small coin or medallion, bearing an organization's insignia or emblem and carried by the organization's members. Traditionally, they might be given to prove membership when challenged and to enhance morale. Some challenge coins have created controversy and their creators have been Front and back of the 30th Anniversary Commemorative MST3K Challenge. The 2011 US Army Commemorative Coins are the first of two commemorative coin series released by the United States Mint in 2011. The gold, silver and clad. What is it'The 2011 Army Commemorative Coins consist of a five dollar gold coin, a silver dollar, and a copper-clad half dollar that the U.S.Mint is offering during.