Last year I purchased a 500sl in nice shape.
After driving it a short while I noticed the tach / speedo / odo
rellationship was not what the published specs stated.
I made some trips down the road side by side with other cars
and over a measured 4 mile distance and confirmed my suspicions.

I bought another cluster from a known 500 sl and the problem went away.

Prowling this forum I learned (i think) there are 32 different calibrations for this cluster unit. When I removed the first unit I noticed someone had written
tested ok in a green marker.

I would like to have the unit tested and calibrated as I suspect it may have come from a 6 cylinder ir even another model.

Is there a knowledgable mechanic out here that can give me some advice?