Compass, Aperiodic, US Military Aircraft, Pioneer 1811-1-D
This appears to be a post WWII Direct Reading Aperiodic Compass used at the navigators station in US military aircraft. Made by Bendix, part number 1811-1-D. It appears to have never been put into service judging from its superb condition. An aperiodic compass, after being deflected, returns by one direct movement to its proper reading, without oscillation.
It is similar to a WWII-era D-12 compass, which was typically mounted on the navigator's desk. It has a rotating dial with directional markings, which would be rotated to align with the compass card floating in the reservoir below it. On this model, there is a locking screw that captures the rotating ring and preventing unintended rotation. It is also an illuminated compass, with a silver connector and two 3V lamps in place just below the top red pointer.
Measures ~6 inches diameter and ~4 inches in height. The glass and case are intact, and the compass fluid, while slightly dark, is fully present. We welcome knowledgeable visitors to share what you might know about this compass.