Gyro Horizon OV-1 It is in terrific condition

It is in terrific condition given its age

From Air Navigation Technical Manual TM 1-205 1940 US Army Air Corps (the reference call-outs refer to the diagram in the photo gallery reproduced from this manual):

A colleague offers this explanation of its operation:

The compass card containing the markings of the compass rotated to indicate magnetic north as it received signals from the master unit (in the Lanc

As an offshoot of this equipment Ryan have also developed a helicopter hovering aid (AN/APN-97) which presumably uses Doppler signals to tell the pilot whether or not his machine is stationary above ground or sea

Gyro Horizon OV-1 It is in terrific conditionThis is a pre WWII era Gyro Horizon (Flight) Indicator, Army Type C 5, made by Sperry, part number 643770, marked for the Air Corps US Army. This indicator has a serial number prefix "AC 40", evidence of a manufacturing year 1940, prior to the US entering WWII. The C 5 Gyro Horizon was used across all aircraft of the US Army Air Corps, including bombers B 17, B 24, B 25, fighters P 38, P 40, P 47, P 51, and transport C 47. The Gyro Horizon provided