The original speedometer was an 80mm Jaeger chronometric instrument, reading to 100 mph.  (The 80mm refers to the diameter of the case, or the hole it fits into.)  There are various Jaegers that look vaguely similar but are incorrect, in particular the ones with magnetic mechanisms, which have the zero at bottom left, the 5-digit odometer below the needle and the cable drive in the centre of the rear case.   Chronometrics have the drive off-centre.  100mph chronometric speedos are rare but 80mph chronometrics are readily available and can be recalibrated and fitted with replica 100mph dials.  

Click on thumbnail to view higher resolution image.  Right-click to save to file.

An original 100 mph Jaeger speedo on Chassis 7308.

Zero is at top right, and the 5-digit odometer at the top, as is correct for the original instruments.

Restored speedo of correct pattern.

From Chassis 7315.

A high-resolution image of a 100 mph Jaeger speedo.

Photo of the same instrument as the preceding one, under softer lighting conditions.

80 mph Jaeger speedo.

Fitted to Chassis 7313.