Ball Turret Azimuth Position Indicator, B-17, B-24 B-29 and US Navy's PBY5A Catalina

and US Navy's PBY5A Catalina and PB4Y Privateer

the calculator measures ~8 inches by 6 inches by 1/2 inch thick

Used in most US bombers during WW2

the AN-104-series is the most common US VHF aircraft mast of WWII

The E-4 System was used in the late 1940-1950's and was still in use in some 1960's aircraft

Ball Turret Azimuth Position Indicator, B-17, B-24 B-29 and US Navy's PBY5A CatalinaThis is a mechanical Ball Turret Position Azimuth Position Indicator, Sperti part number 11585, used in the Sperry ball turret in WWII era heavy bombers such as the B 17 Flying Fortress and B 24 Liberator. Mounted within the ball turret at the right foot of the ball turret gunner (see photo), it was connected to a rotating mechanical control cable. The round turret silhouette in the center of the dial rotated as the turret rotated relative to the