By Betta Manufacturing Company, Enfield. Stores reference 6B/166. Approximately 14.5cm diameter. Circular white metal instrument with rotating discs for setting the ground pressure, temperature, indicated height and airspeed. For use with ICAN calibrated altimeters. Used by Navigators when plotting routes etc. Well marked with both King's crown and war department broad arrow. 1943 date code. In excellent unused/unissued condition with original stores tag, waxed paper wrapping and re-packaging box dated 1947. Stock code M16492.