I have rebuilt the speedometers in my 1950 Chevy and 1952 GMC trucks and used the instructions found here:
http://chevy.oldcarmanualproject.com/bulletins/ums/52UMS3d42501.html In resetting the odometer after installing the new decals, I wanted to return it to the original mileage. I found that it was best to start by setting all the numbers to zero and then by starting from the left most number you could hold your finger on the tab on the small metal disc while rotating the adjacent wheel until the far left number was on the desired number. As I adjusted the second number from the left, I held the two left most tabs stationary as I rotated the third wheel. Do this in turn with each of the wheels working your way from left to right until you have all the numbers registering the desired mileage.
