From ACO catalogue: " The compass, known as Pattern 27P, is mounted in a binnacle, Pattern 51P, in the conning tower. Two 6 volt lamps are mounted above the compass in such a manner that either may be swung over a condenser lens. This movement was effected by means of a rod passing through the hull. In this exhibit only a short operating rod is shown. The movement of the lamps also switches on the appropriate one. The image of the card is projected by the lamp through a system of prisms and lenses to a ground glass screen before the helmsman inside the vessel. For steering when on the surface a glass window is let into the binnacle cover and a third light is provided for lighting the card from below...."
Binnacle: Fitted with sphere brackets and spheres; racks for fore-and-aft and athwartship corrector magnets, and provision is made for vertical corrector magnets.
O.A. height of binnacle 34.0" (86.3 cm)
Lenght of projector tubing 119.0" (302.2 cm)