Free Air Temperature Indicator, Direct Reading, Type C-13B WWII
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. It would be held in place by the accompanying screw-on external shroud.
Most uniquely, this instrument has the letters embossed on its face "A.F. U.S. ARMY", which stands for Air Forces US Army(difficult to see in photos). The Air Force US Army was the predecessor to the US Air Force. It has a serial number prefix of AF43, evidence of a 1943 year of manufacture.
It is in very good condition given its age. The dial markings are clear and the glass intact. The temp reading is likely inaccurate, nonetheless it is a nice artifact of the era. Measures 2in diameter and 3.5in long. See photos.