Liquid compass.

Bowl: Cylindrical grey painted metal, filler plug at side, expansion chamber at base. Has a protruding rectangular window fitted to aft side in addition to the circular verge glass on the upper face. The verge ring is graduated to 360 degs anti-clockwise and a course indicating pointed is fitted at the centre of the glass. An electric lamp is fitted to the side of the bowl. Inside of bowl is painted white. A lubber, painted black, line is on fore side of bowl and a thick wire lubber line is fitted beneath a rectangular window at the side. Mounted by two lugs attached to the side of the bowl on two vertical pillars to a circular wooden stand, diameter 7.75" (19.7 cm)