Liquid compass
Bowl: Brass, grey painted, fitted with filler plug at side and an expansion chamber at base. The bowl is set in an outer case having provision for vibration damping. Inside of bowl painted white. Fitted with a black wire lubber line. Has a glazed rotatable verge ring which is marked with a red triangle at North point, graduated to 360 degrees. Verge ring carries two parallel black wires, for grid steering. Fitted with a locking device to prevent verge ring from rotating when not required.
Card: White plastic(?) spider of four elements which are marked in black, the North point is indicated by a black arrow.
Needle: Two needle magnets slung beneath the card.
Pivot: Unsighted but possibly of the inverted type, with the pivot stem attached to base of bowl on a small disc.