US Air Force Association 1947-2008 Challenge CoinMeasures Approximately: 1.75 InchesNo Special EdgingFront: Air Force Association 1947-2008, Then and now the force behind the forceBack: Air Force Association Mig Alley ChapterChallenge Coins are generally created for the Military and are prized by the service members that receive them. Perfect for Collectors of Militaria.