IF the cluster and speedo design is the same as my 200E, then it may be a simple fix.
Without disassembling the cluster, look at the odometer, if it looks like it's skewed, the right hand side lower than the left hand side, then it has just jumped gears. All it needs (hah!) is that you take out the instrument cluster, remove the speedometer module and push the spindle back in, and it should engage the gears and work well again.
IMHO, it was a bad design, but it's usually due to the trip meter getting sticky, and if you press the reset button, all the number may not line up properly at "0000", if so, it will jam and cause pressure to build up on the drive spindle, which then derails and thereby dislodging itself. Somebody should have put a friction clutch on the trip meter drive gear.
While it's out, I would clean and lube the odometer and trip meter gears as well.
Getting the cluster out:
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Getting the speedo module out will require that the tacho module (on the left in the picture:
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loosened and the light dimmer control (white ceramic part) be removed as well.
Nearly if not all German postwar cars use the same VDO mechanism which has as a weakness one gear that ALWAYS (eventually) fails.
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sells just the gear and it's the only placeto get it. It's pretty easy to take the thing apart and replace itand it should be good for another 20 years at least. Some hopefully usefull instructions for getting the thing out are here:
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