Free Air Temperature Indicator, Direct Reading, WW2
This is an authentic vintage Direct Reading Free Air Temperature Indicator made by the Rochester Manufacturing Co., PN 1592, as used in Bombers Boeing B-17 Flying Fortress and Consolidated B-24 Liberator, plus Transports Douglas C-47 Dakota 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 thru the skin or the windshield of the aircraft.
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. So this instrument is likely from Air Force US Army aircraft i.e., pre 1947. It also states "Property of US Army Air Forces" on its rear.
It is in terrific condition given its apparent age. The dial markings are clear and the glass intact. The temp was accurate on the day the photos were taken, but it has not been tested at its extreme ranges and therefore its accuracy across its range is unknown. Measures 2in diameter and 3.5in long. See photos.