Suction Gage, AN 5771-5, US Army Air Force WWII C-47 The knob would rotate the

The knob would rotate the face of the dial while the pointer remains fixed to set the present field elevation

It has a service label from the US Air Force Tinker Air Base's OCAMA (Oklahoma City Air Materiel Area)

base plate

At almost 200 pages

the difference between the totals is the difference in density of the two fuel types

Suction Gage, AN 5771-5, US Army Air Force WWII C-47 The knob would rotate theThis is a WWII era Suction Gage, AN 5771 5, made by Collens. This indicator has a serial number prefix "AF 43", evidence of a manufacturing year 1943. The AN 5771 5 Suction Gage was used across all aircraft of the US Army Air Corps, including bombers B 17, B 24, B 25, fighters P 38, P 40, P 47, P 51, and transport C 47. The Suction Gage measured the amount of vacuum generated to power the pneumatically operated gyroscopic instruments, such as the Gyro