Consists of a grey-painted circular metal base, with which is a rotating verge ring encompassing a central bearing plate. The verge ring carries two hinged sight vanes. Fore sight has a sighting wire and dark glass reflector. Bak sight has a slit and pinhole, and is fitted with two shades. A metal tab projecting from the fore sight mounting carries an engraved lubber line. A second lubber line is also engraved on the inner circumference of the frame. The bright metal bearing disc has black markings and is graduated quadrantally in degrees. Cardinal and half cardinal points are marked, and there is a decorated N point. Fitted in grey painted gimbal ring which is secured to box by two brackets. A heavy "mushroom" balancing weight is suspended on a rod beneath the frame. In fitted wooden box 8 x 8 x5.6" (20.2 x 20.2 x 14.1cm) with leather securing strap.