Ok.. at the risk of being laughed at... please see attached picture. This is also a Leica 50mm/2 Summicron. Look at the inner copper ring, you can see it through the nickel colored bayonet curve. This is not true on my lens (see photos in 1st post). The inner copper cylinder on my lens seems to have been shaved down. I'm not talking about the machined curve in the lens mount, i'm talking about the copper colored ring behind it. The copper ring in this photo appears to be the same height all the way around, on mine it's shaved down to follow the curve of the mount.