Free Air Temperature Indicator, Direct Reading, Type C-13B WWII (Irreparable)
This is an authentic WWII-era Direct Reading Free Air Temperature Indicator Type C-13B, as used in Bombers Boeing B-17 Flying Fortress and Consolidated B-24 Liberator, plus Transport Douglas C-47 Skytrain and others. The instrument indicated to the pilot the aircraft's external air temperature from -70dC to +50dC in aircraft of the Air Force US Army, and would have its stem installed from the cockpit or the bombardier's compartment thru the skin or the windshield of the aircraft.
This instrument is marked Property US Army Air Forces, which was the predecessor to the US Air Force during WWII.
Unfortunately the interior glass is dirty and cannot be opened to clean without damaging the rolled rim. The temp reading is likely inaccurate, nonetheless it is an authentic artifact of the era. Measures 2in diameter and 3.5in long. See photos.