Autopilot Trim Position Indicator, USAF E-4 System,, C-130, 154372

This 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 and the case is intact. Measures approximately 3.25 inches diameter and 2 inches deep.