Boost Pressure Indicator, MK IIIm, 6A/1581, British Royal Air Force, 1943 C-121 it is marked for the

it is marked for the Inboard fuel tank

The knob and card are a bit sticky

and fighters P-38 Lightning and P-61 Black Widow

Measures 5

or film spools

Boost Pressure Indicator, MK IIIm, 6A/1581, British Royal Air Force, 1943 C-121 it is marked for theHere is a WW2 era Boost Pressure Gauge, 7 to 25 PSI, used to indicate the supercharger power being delivered to the engine when demanded. Used in Merlin powered RAF, RAAF, and RCAF aircraft. According to the RAAF 346 Types and Locations of Instruments in RAAF dated 1945, the 6A 1581 appeared in the DeHavilland Mosquito. This is New Old Stock in its original box dated 1943. Mint condition gauge.