Drift Sight, Tail, RAF Mk IV Kit Ref No 6B/110, 1939 Viscount There were two complete M6

There were two complete M6 periscopes in brackets on the turret walls

and ~4 inches and 5 inches wide

These were often carried aboard aircraft as emergency back-ups in these latter decades in the event of failure of the more sophisticated navigation computers that emerged in the 1960's and 70's

The P2V was retired from survey use in June 1954 after having flown approximately 60 000 nautical miles of survey track over the North Atlantic Ocean

intersecting them along the specified firing range

Drift Sight, Tail, RAF Mk IV Kit Ref No 6B/110, 1939 Viscount There were two complete M6Here is a WWII era Tail Drift Sight, Mark IV Kit, as used in bomber and transport aircraft of the British Royal Air Force with navigator aircrew, such as the Avro Lancaster, and likely used in other bombers such as the Vickers Wellington and Short Stirling. This kit includes the optical periscope, a base plate, and the aluminum drift plate that screws onto the base plate, and wooden carry case with leather strap. Stamped on the label on the case of