I have a very much related question, I think. With a 1955 M3, is there a way to make the second patch image more visible? That's the one that moves as the focus moves. My recently acquired one is so similar in contrast to the base patch that stays fixed, that I'm having a terrible time focusing the camera in everyday lighting conditions. I find it almost impossible, and not due to an eyesight issue because mine (corrected by glasses) is good enough to manually focus a dim f/8 lens in a small APS-c DSLR viewfinder for birds in flight.
Could it be improved by a CLA - Clean, Lubricate, Adjust - job at a repair shop? Is that necessary?