Just a random thought, but if the Odo has not been replaced, the higher numbers are exposed to sunlight longer than the lower ones. Compare the discoloration of the left-most roll and see which one has never been exposed to the elements. Subtract from there.

Might be a starting point. Or not...

Jim



1957 Chevrolet 3100 Stepside
235, 3-speed w/OD
In the Stovebolt Gallery