Compass, Direct Reading Magnetic, Type B-16, 1818-4-A
Here is a Direct Reading Magnetic Compass Type B-16, which was used across nearly all bomber, fighter, transport, and trainer aircraft of the US Army and US Navy. This compass was typically installed at the top of the windscreen or on the instrument panel, such as seen in B-17's, P-38's, and P-51's, and many others.
This example has a serial number prefix of AF-43, evidence of the 1943 year of manufacture. The compass still contains its damping fluid and the compass card rotates freely. The knob at the top of the face is the light bulb which would illuminate when turned if affixed to the correct power supply.