Radar Indicator, CS-55ACE, ASD Surface-Search, WWII US Navy Eurofighter Typhoon The crystal glass was secured

The crystal glass was secured by a bezel and gaskets to seal the movement against dust

It has a calibration mechanism

See photo of the location of the instrument on the Flight Engineers upper instrument panel from the C-121 flight manual dated 1958

This periscope appears to be new old stock

Radar Indicator, CS-55ACE, ASD Surface-Search, WWII US Navy Eurofighter Typhoon The crystal glass was securedThe indicator is a CS 55ACE indicator for a WW2 US Navy Type ASD surface search radar system. The ASD was the first effective American microwave search radar, and was used in aircraft such as the US Navy's Patrol Bomber Lockheed PV 1 Ventura, PV 2 Harpoon, and Grumman TBF Avenger. Researching the internet reveals that Type ASD X band airborne search radar used this indicator as a B scope (range vs bearing) in US Navy patrol aircraft to detect ships