Compass Bowl, for Direct Reading Compass, WWI
Here is a Compass Bowl from a WWI-era aeronautical compass.
The brass bowl would have been mounted by the 3 rubber-covered metal pegs to a frame, with the frame attached to the instrument panel or to a pedestal. The compass card, which is missing, would rest on the center spring-mounted pole, allowing it to float in the compass fluid and to rotate as necessary to point north. There would have been a directional ring affixed to the top flange which would be rotated to assist in course setting. It may have been electrically-illuminated with a small lamp mounted at the round side window next to the intact wire 'lubber line'.
There are some raised degree markings on the inside bottom of the bowl.
Measures ~5 inches diameter and ~2.5 inches tall.