Date registered: Dec 2005
Vehicle: W211 E320 Bluetec R129 SL500 - $1300 car ........ Ford F350 6l
Location: CA Bay Area
Mentioned: 9 Post(s)
Quoted: 1127 Post(s)
I've been rotating those mechanical odometers both ways. Even had couple spares, but dispose them couple years ago. (4 years after I sold W123).
However it is easy to damage the odometer if you are not too carefull, so another way is to take a picture of both odometers with current newspaper in the back and just install the good one keeping the record of mileage change.