speedo part number

[geoffreymbrown]

I recently acquired a 250d with a bad odometer however a brand new
speedo came with the car. I'm having a hard time figuring
out if the new speedo is a correct replacement.

The old speedo is

A 124 542 17 06 (0-140mph)

The new one is

A 124 542 79 68 (0-120mph)

I have the epc subscription allowing access in international cars,
but there doesn't seem to be a way to find out which speedos work
with which rear ends (I assume that's the key criterion).

I suppose I can test it with a gps, but I'd still like to know how
to look such things up properly