i have only rebuild around 35 of them over the years and on a good few i deffo see the friction wear marks on them as discoloration so was curious and checked them with my digital gauge and it was fractionally thinner where the discoloration is compared to the edge where the 2 bearings cup half meet so me thinking wear down ? thats great that tha is your job next time i have a tehnical Q i can pm u :) i only learned it by doing it at home