I have two copies of the 50/F2 AI, and got that the first is an earlier one, and the second not one, but had no others to compare with it. I have the earlier version shown on the left, and a later, 3-screw version, which is essentially similar except for the flange screws, with the thicker upper boss (name not known) and the double-spanner threaded rear lens mount.
I've never had a factory-converted AI lens, only home milled conversions, but assume that those also did not have the lens speed post, since certain AI cameras like the F4 disallow all conversions from the matrix metering function.
I don't use these much these days since I'm using DX, and have the 16-80 which is grand for traveling, but back in film days this was a favorite, one of those lenses that's just inherently good at everything. I have not raced my two to see if there's a sharpness difference, but now that the subject is raised, perhaps I'll give it a try.