Compass, Magnetic, Type B-20 Vertical Card, WWII, US Army Air Force Vulcan then the larger pointer indicates

then the larger pointer indicates RPM around the outer scale from 50-110%

a microphone trigger switch

the small circular window between its 6 o'clock and center position changes from red (set-on)

Both operate as they should mechanically

The part numbers have been confirmed in the TBM Avenger Erection and Maintenance Manual dated August 1945

Compass, Magnetic, Type B-20 Vertical Card, WWII, US Army Air Force Vulcan then the larger pointer indicatesHere is a WWII era Type B 20 Direct Reading Magnetic Compass, made by Autoflight, part number 2221. The B 20 Compass design is unique in that it contains a magnetic horizontal float suspended in damping fluid that engages the directional pointer on a vertical compass card to display direction. The pointer indicates the direction of aircraft flight. The knob in the lower left corner manually rotates the course indicating pointer (i. e., the two