Speedometer, M-4 Sherman Tank, #6208454 US Army A4 Skyhawk It is in very good

It is in very good condition given its age

This is an example of an Autopilot Slaved Gyro Magnetic Compass

and resetting is simplicity itself

The pointer indicates BMEP as received electrically from a transmitter mounted at the engine

according to their flight manuals from the 1950's

Speedometer, M-4 Sherman Tank, #6208454 US Army A4 Skyhawk It is in very goodOk, 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