A reader informed me that there are actually two different versions of the Leica Super-Elmar-M 21mm f/3.4 ASPH lens (product number 11145). Here are the details:
First, this is the Leica Super-Elmar-M 21mm f/3.4 ASPH lens version 1 (pictures from B&H):
I was told that this first version would bind up when focussing and was recalled by Leica soon after the official release. The recall was voluntary and there are probably still a few pieces out in the wild – perhaps future collectibles?
Leica then replaced the lens with the current version that the area at the mount-end thickened – here is the new version and you can clearly see the difference in the depth of field ring (pictures also courtesy of B&H)::
I happened to have the new version – here are a few more pictures:
As far as I know, both lenses have the same product number. Even the official Leica website still shows the old version 1.