Airspeed Indicator, 500 MPH PN386-024 Type D-4
This Airspeed Indicator is a WWII-era US Army Air Force Type D-4 as used across a number of US Army Air Corps and Air Force aircraft during WWII, including heavy bombers B-17 and B-24, medium bombers B-25 and B-26, as well as light bomber A-20, according to the Maintenance Interchangeability Chart dated Dec 1943. It was also used in versions of US Army Air Force WWII fighters P-38, P-39, P-40, P-47, and P-51.
There appear to be two designs of the D-4, one with a diving speed marker and one without. This one is without it. The example here displayed airspeed up to 500 MPH on two scales. The pointer rotated clockwise to indicate airspeed up to 300 MPH along the outer scale, and then continuing from 300 to 500 MPH on the inner scale. The indicator was illuminated by a small 3V lamp at the upper right corner once twisted to make contact within it socket, but it is no longer in place.
It is in very good condition given its age. The dial and glass are intact, although the lens is missing its seal and does move slightly. Measures 3.25 inches diameter and ~ 2.5 inches deep.