Aerial Machine and Tool
Pelorus, Aircraft, US Navy Mk I 18-P-21690
This is a WWII-era Aircraft Pelorus Mk I used by air navigators in the US Navy. The Pelorus was used for taking bearings on objects of interest, be they celestial or terrain.
The bearing sight (the cross bar) can be inclined or declined on its center axis, and rotated to the desired bearing which can be read on the base scale. Drift angle can also be determined.
Measures approximately 5 inches diameter and 4 inches tall.