Autopilot Trim Position Indicator, USAF E-4 System,, C-130, 154372 C-46 it would have the small

it would have the small air filter AN-5821-1 attached to its rear top port

The liquid has since evaporated

and a master switch in the center

This has been confirmed in the F-80 Illustrated Parts Manual dated 1958

The luminous markings have turned color with age

Autopilot Trim Position Indicator, USAF E-4 System,, C-130, 154372 C-46 it would have the smallThis is an example of an Autopilot Trim Position Indicator, Type O 2, for the USAF Autopilot Type E 4 (aka as the Sperry A 12 Gyrosyn Automatic Pilot System). The E 4 System was used in the late 1940 1950's and was still in use in some 1960's aircraft. Lockheed C 130 Hercules and C 121 Constellation transports used this system, as well as civilian aircraft such as DC 3 and DC 6. The Indicator is in exceptional condition for its age. The glass is clear