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.
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