This looks like a Smiths PA, or at least one of that family. It's probably from an Austin 7. These centrifugal speedometers were made in two styles, a rear drive which has a cranked bottle-shaped back to it making it 5" or so deep, and a parallel drive, where the drive enters the side of the casing parallel with the glass 1" below the glass. The parallel drive ones went into petrol tanks where the drive cable ran through a tube in the tank down to a take-off on the gearbox.
If you locate a source for a an 80MPH dial face and a means to re-calibrate them, please let me know!
JFerg