Description US Navy pelorus in wooden storage/carry box. -Yellow metal plate on outside of box: BUREAU OF SHIPS U.S. NAVY STANDARD PELORUS 7 1/2 INCH ILLUMINATED DIAL Mark III, MOD. 0, SER. NO 3009 CONTRACT NO NOs-88774 1941 KELVIN & WILFRID O. WHITE CO.. BOSTON -#3009 written on top lid of box -Box has two metal handles on either side -Compass has black metal cover -Compass white w/black lettering -Sight valve clamp attached -Power cord attached at bottom -Set up instructions stapled on inside of box A pelorus is a magnetic compass with a vane for measuring the bearing to an object. It is used on the deck of a ship to quickly measure the true bearing (angle from north) or relative bearing (angle off the ship's bow) to a line of sight. It can be used in pilotage, or navigation by sighting landmarks when within sight of shore.