The BCT Challenge coin incorporates the American eagle, our national emblem since 1782. It symbolizes long life, great strength, majestic looks, sharp vision, among others. The Eagle is used by multiple organizations within the Defense Department, including NSA. BCT is proud to incorporate the noble Eagle into its coin.
Challenge coins have been a tradition in the military for centures. In the U.S., they became established during World War I. More information is available here:Wikipedia: Challenge Coins