Altimeter, Sensitive, Type C-12, 50,000 ft, US Army Air Force WWII Mosquito Must have been a high

Must have been a high pressure application judging from its construction (number of screws and thickness of lens)

which cross references to those used in RAF aircraft

azimuth and elevation of the identified target and allow the observer to take control if the “blip” was identified as unfriendly

Sweeting’s book "Combat Flying Equipment":

According to other websites which showcase British aviation artifacts

Altimeter, Sensitive, Type C-12, 50,000 ft, US Army Air Force WWII Mosquito Must have been a highHere is an early WWII era Sensitive Altimeter, Air Corps US Army Type C 12, made by Conn, part number 80000. The C 12 Altimeter was used across all aircraft of the Air Corps US Army, including heavy bombers B 17 and B 24, medium bombers, B 25 and B 26, Fighters P 38, P 39, P 40, P 47, and P 51, and transports C 46 and C 47, according to the Maintenance Interchangeability Chart dated Dec 1943. The knob is used to adjust the altimeter to the barometric