Model 15
The 4" Model 15 became the standard Air Force sidearm in 1962. The SAC Elite Guard (Air Police) under Gen Curtis LeMay were the first to receive the M15, and it remained the standard weapon of Air Police/Security Police until replaced by the M9 Beretta in 1990. I know of M15's that had 100,000+ rounds fired through them and kept on going. Gen LeMay was a shooter and gun enthusiast and wanted his cops and all Airmen to be able to hit what they aimed at which is why the Air Force settled on the M15 to replace the GI 45. Several guns were inspired by LeMay and he preferred the accurized .45 for himself and his aircrews although the Air Force never did procure the LeMay .45 that he inspired. From what I know all Air Force Model 15's were marked USAF or Property of United States Air Force. The flaming bomb is the symbol of U.S. Ordnance so I do not believe this is an Air Force weapon, however I saw Model 15's in the hands of Army and Marine aircrews so I know it was used by at least 3 branches. As an aside I also saw a number of 2" M15's in the hands of Air Force crewmen-they carried them as well as several other types of subbies as they fit nicely in the zippered slash chest pocket in the flight suit. I suspect your M15 might have been carried by civilian security personnel at U.S. Ordinance but that's just a guess, it would be interesting to know its history. Still one of the best shooting revolvers I ever held.