Directional Gyro / Turn Indicator, AN-5735-1

Here is a WWII-era pneumatic Directional Gyro/Turn Indicator made by Electric Auto-Lite. According to the Maintenance Interchangeability Cross Reference Charts of the Air Forces US Army, the AN-5735-1 Directional Gyro was used across nearly all aircraft of the US Army Air Force and US Navy during WWII.  

The knob rotates the course setting indicator, and once pulled out, uncages the compass card which would then rotate right or left.  The knob and card are a bit sticky, but not bad given the age of the instrument.