They copied it from the BINI (aka BMW MINI) which in turn copied this idea from a lot of the original 1960s Mini models where owners would quite often add an aftermarket Smiths rev counter to their cars, especially if they were Cooper 'S' models or tuned by experts - e.g. Downton.
EDIT - I have one in my Aygo which I bought after buying the car.
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[I]So long and thanks for all the fish.[/I]
...I used a small (~2") VDO tachometer on my '72 1.6L Kent engined 1972 Pinto; and used two red LED's for lighting instead of single white incandescent bulb.