2012 Veterans' Day display featured the 509th Composite Group. The 509th was the first USAAF bombardment group to be organized, equipped, and trained for atomic warfare. The materials were acquired by 509th crew member, Lt. Cecil N. King, and loaned to the library by his son-in-law Richard Black, director of the Office of Design and Production.
2001 509th Composite Group reunion booklet page 59
393rd Bombardment Squadron Historical records (p59) for Bockscar
Bockscar is the plane that dropped the second atomic bomb, Fat Man, on Nagasaki August 9, 1945.