Amazing flown 6.75 x 3.75 postal cover carried aboard the B-29 Superfortress Dave's Dream of the 509th Bombardment Group on July 1, 1946, as part of the Operation Crossroads Able test that dropped Gilda, a Mark 3 23-kiloton air-deployed nuclear weapon, which detonated over a target fleet in the NE Lagoon of Bikini Atoll with a success rate of five destroyed ships. The cover is stamped "Bombing Plane," with a 509th Composite Group emblem stamp, and a US Navy postmark dated to the Able Test. In fine condition.