Armament & Fields of Fire, Luftwaffe Aircraft USAAF Training Manual French Armée de l'Air It has a service label

It has a service label from the US Air Force Tinker Air Base's OCAMA (Oklahoma City Air Materiel Area)

The remaining pages describe the aircraft of each nation's air services

so likely from a US Navy or US Air Force aircraft

with BU AERO US NAVY embossed in very small letters on the center of its face

The housing had been repainted at one point

Armament & Fields of Fire, Luftwaffe Aircraft USAAF Training Manual French Armée de l'Air It has a service labelHere is an authentic original WWII era training brochure, "Armament & Fields of Fire, German Aircraft", published Dec 1942 by the US Army Air Force. This simple manual lists and illustrates the location of armament of 20 armed aircraft of the German Luftwaffe in service by 1942, and the fields of fire of each gun carried by each aircraft. This information was critical to pilots of US fighter aircraft and aircrew of bomber and transport aircraft as