Altimeter, Sensitive, Type C-12, 50,000 ft, US Army Air Force WWII DC-3 a radio freguency carrier which

a radio freguency carrier which is frequency modulated at a rate of 120 cycles per second between the approximate limits of 420 and 460 mc on the low range (0-400 feet) and 443 to 447 mc on the high range (400-4000 feet)

Pollywogs became Shellbacks

We have not tested it

leaving witness marks on the inner glass

or Elevator/Nose Position Indicator

Altimeter, Sensitive, Type C-12, 50,000 ft, US Army Air Force WWII DC-3 a radio freguency carrier whichHere is an early WWII era Sensitive Altimeter, Air Corps US Army Type C 12, made by Kollsman. 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. It has a serial number prefix AF 43, evidence of a manufacturing year