Autopilot Mk 10 Series
Apart from the prototype marking it would appear to be one of a range of available control units for a Smiths Mk 10 Automatic Pilot as fitted to a wide range of 50s-60s RAF aircraft, eg, Valiant, some Canberras, Vulcan Mk1, Victor Mk1. Similar units were fitted to the Mk 10A, 10B & 10C Autopilots fitted to Argosy, Vulcan Mk2, Victor Mk2, and Hercules (C130K for the RAF).