This reference photograph documents a graduated display of ammunition calibers encountered during the Vietnam War, from large-bore 37mm anti-aircraft cannon rounds down to a .38 caliber pistol round and a small flechette dart. Such comparison displays were commonly assembled at air base armories and intelligence sections to train personnel in the rapid visual identification of both U.S./NATO ordnance and Soviet/Warsaw Pact-pattern rounds recovered from the battlefield or used against allied aircraft. Project: 219011