Pilot Director Indicator as used with C-1 Autopilot, WWII B-29, B-24, B-17 (A) F9F Cougar and the bubble is full

and the bubble is full and intact within the glass chamber

measuring ~4 inches by ~7 inches

The interior glass has some spots that could be opened and cleaned

The fluid is gone

Pilot Director Indicator as used with C-1 Autopilot, WWII B-29, B-24, B-17 (A) F9F Cougar and the bubble is fullThe Pilot Director Indicator (PDI) was used during WWII in bombers of the US Army Air Force, including heavy bombers B 17 Flying Fortress, B 24 Liberator, and B 29 Superfortress and medium bombers B 25 Mitchell and B 26 Marauder, and US Navy's PBY5A Catalina and PB4Y Privateer. The PDI was located on the pilots instrument panel, and received signals from the bombardier to indicate his desired course changes, left or right, to obtain an accurate bomb