Circumferentor. The box is marked NAV1373.1 and can be found via the Whole/Part toggle.
Complete circle of engraved brass with four fixed sights, universal socket, and base ornamented with heads of monsters. Scale marked in 30' divisions. Black leather case.
Often referred to as a "surveyor's compass"; its compass allows bearings to be taken using magnetic north. This type of instrument was later used in mine surveying.