BMEP Gauge- PBY/PBM-5/P-2 JRM-1 Martin Mars- Kollsman 647K-02

Offered in this listing is an authentic Engine BMEP Gauge from the late 1940's, made by Kollsman PN 647K-02. The body of the instrument has a label of the US Naval Air Station Coco Solo, Panama, (see photos, hard to discern, but I've sold 3 from this lot which are identical to this one including the label), and may have been installed aside others like it in a large multi-engine piston-powered aircraft. I have located this instrument on the engineers panel of the US Navy's floatplane JRM-1 Martin Mars, in its flight manual dated 1947.  Only 7 were ever built. The face is embossed BU AERO US NAVY (i.e., Bureau of Aeronautics US Navy). 

NAS Coco Solo housed several Patrol/Patrol Bomber aircraft during its tenure, including PBY Catalina's, PBM-5 Mariners, and P2 Neptunes.

BMEP is the acronym for Brake Mean Effective Pressure, and the gauge measured each engine's crankshaft torque by measuring oil pressure in the engine planetary gear drive system. This type of gauge was the primary tool used to lean the large radial engines in service late in the piston-powered aircraft era.  BMEP is no longer measured to monitor engine performance, achieving the same results by monitoring EGT (exhaust gas temperature).