Hi Erik,
Apologies if I appear mysterious, it was not my intention.
From the cameras that I have seen, the chrome finish on the latest, like a IIIg or late IIIf, is slightly 'frostier' and has a sharper grain than earlier cameras. Nothing to do with wear. The shutter release and rewind lever on your camera have this finish, it is a bit like an M. Also the shutter release collar and the button, although of course of the correct pattern (for the period), have a sharper outline or profile.
Erik, to be honest, I may be talking complete and absolute rubbish. But I sent a black III back to Leica in Mortimer Street in the 1960s when the button fell off. They replaced it free of charge with one exactly the same as that on your camera. I only recently changed it for something more appropriate.
As you know, many of the smaller components change subtly over the years as does the finish. Prewar chrome is different from wartime and early postwar chrome (which deteriorates). Later chrome has a slightly different grain, colour and finish.
I won't be upset if you or anyone else tells me that my observations are trash but I would be happy if someone agreed. I can't reallyoffer to illustrate the point since I have now sold off all my chrome cameras (apart from trusty M6) and no longer have examples to prove the point.
Best
Michael