Binnacle hood for an Admiralty Transmitting Magnetic Compass Mark 11 (ATMC11), with two arms for the soft iron correcting spheres (which are missing) and a top that can be clamped shut. The ATMC11 was a modifiied version of the ATMC8, which was designed for submarines and had a watertight binnacle fitted in the fin. The Mark 11, intended for nuclear submarines, had degaussing correction and was first installed in HMS Valiant (launched 1963). This hood is the one used in HMS Valiant. Magnetic compasses proved unsuitable for nuclear submarines and were subsequently withdrawn.