Oil Pressure, Dual, Set for 4-Engine Aircraft, Type B-9A
Here is a set of WWII-era Type B-9A Dual Oil Pressure Indicators, as used in four-engine of the US Army Air Force such as bombers B-17, B-24, and B-29 and transport C-54. These are Bendix Autosyn indicators, which used pressure sensors at the engines which electrically transmitted the signal to these electrical indicators. Both are labeled "AF US ARMY" on their faces. The indicator marked for engines 3 & 4 has a 1944 manufacturing serial number prefix. These were also used in twin engine aircraft of the US Army Air Force such as B-25, B-26, and C-47, but with markings for engines 1 & 2 or L & R.
These indicators are in exceptional condition given their ages. The lettering is precise, the glass is clear and case intact. Measure 3.25 inches diameter and ~5.5 inches deep.