Compass, Magnetic Direct Reading, US Navy Mark IX Carvair While the B-6 may have

While the B-6 may have been used in some versions of dual engine aircraft such as fighters P-38 or P-61

According to the Maintenance Interchangeability Cross Reference Charts of the Air Forces US Army

The caging knob pulls out and turns to cage the gyro as it should

The US Navy's TBM Avenger Torpedo Bomber also used this venturi

12 April 1957

Compass, Magnetic Direct Reading, US Navy Mark IX Carvair While the B-6 may haveHere is an example of the WWII era US Navy Aircraft Direct Reading Magnetic Compass Mark IX, as used in the seaplanes PBY Catalina and PBM Mariner Patrol Bombers. The compass was illuminated electrically via bulb mounted in a small compartment over the compass itself. Inside the same compartment is access to the direction compensating screws, used to calibrate the compass. This example is in reasonable condition for its age. The fluid is absent.