Brass bowl set in gimbals. Centre of bowl has graduated plate (quadrantally in degrees) revolving a centre pin. About the centre plate revolves an azimuth circle, carrying sight vanes ( fore sight has sight wire and reflector glass, aft sight is fitted with slit and two shades). Also fore sight has a lubbers arrow toe nable bearings to be read off. The wooden base is fitted with an electric lamp, for use in submarines.