exact item shown, This unit is missing glass, and heading knob pictures show front, back, label with serial number. This is a synchro device, there is a link to the operator's manual after the description with the yellow background.

Radio Compass Indicator, I-82-A, of SCR-280-A & AN/ARN-7 System, Signal Corps US Army

The Navigator's Radio Compass Indicator, I-82-A, was a component of the SCR-280-A and the AN/ARN-7 Radio Compass System. These systems were used in versions of the WWII-era Air Corps US Army Douglas C-47 Skytrain transport, according to the US Air Service Command's Airborne Radio Equipment Handbook dated 1943, and in US Army Air Force bombers B-17, B-24, B-25, and B-26.
The radio compass, receiving ground signal from a selected transmitter via its loop antenna mounted top or bottom of the fuselage (see photo of an example of the loop antenna), provided directional indication (left or right) to the pilot and the navigator with respect to the source of the signal. The knob at the top right allowed the navigator to adjust for the desired course relative to the signal received from the radio compass.
Measures ~5 inches diameter and ~4 inches deep.

the operating manual for the equipment is located here: https://www.aafradio.org/docs/ARN-7_operating.pdf

Note to me: shoe box under analyzer bench

I normally ship within 24 hours of your order, but the post office does not always initiate tracking when I put the packages in the drop off box.

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