This compass, for which Schilovsky claimed vast sums from the War Office, consists of a bare compass needle in a shallow metal bowl 1.75" in diameter inside a larger wooden one 2.75" diameter gimballed in a wooden container. It was intended to turn the tank on to each magnet heading in turn and then mark on the broad verge of the bowl, opposite the end of the needle, the distinctive letter for the heading. These letters were printed on paper and stuck on.