Identification unit contactor. This US manufactured BC-929-A Rebecca interrogator indicating unit was based on a design taken to the US in 1940 by the British Technical and Scientific Mission lead by Sir Henry Tizard. The mission, which became known as the Tizard Mission, sought US and Canadian help with developing and manufacturing British technology at a time when British resources were taken up with the war effort. The Rebecca unit works with a Eureka beacon to guide aircraft to the beacon's location. Photographed at the Office of Naval Research 75th anniversary commemoration of the Tizard Mission, at the Canadian Embassy, Washington DC, USA, on 17th November 2015.