Speedometer, M-4 Sherman Tank, #6208454 US Army

Ok, yep, this isn't aeronautical, but it's certainly an interesting item nonetheless.  

Here is an example of a Speedometer of the type used in the WWII-era US Army M-4 Sherman Medium Tank, made by the AC Spark Plug division of General Motors Corp.  The US Army part number 6208454 and GMC part number AC1567470 appear on the face of the instrument.  The 6208454 number is referenced by the Sherman tank's technical documentation/illustration, see 2 photos in the gallery, from our friends at The Sherman Tank Site. Although the image of the instrument panel shows an instrument without the tripmeter reset knob, that illustrated speedometer does show a tripmeter so it only goes to assume that it had to have a reset knob like the one in our example.

The face is plexiglas and is a bit scratched, but perhaps not surprising for an artifact of its age.  The tripmeter reset knob is bent just a bit.  Clearly not new-old-stock, which makes it even more interesting since its seen 664 miles of service.  Or maybe that was just while filming Fury.... (just kidding, of course).

Measures ~ 4 inches diameter and 3.5 inches deep.