as noted above, all the MK II grips will work on each other, except for the 22/45 or if the upper ( receiver) may have been installed onto an earlier MK I frame, see this done from time to time, or vice versa........the MK II has the cutout ,notch, at the top of the LEFT panel to clear the hold open lever, MK I does NOT......
MKI's ( and standard autos) have two different hole patterns in the frame ,A-54 and the later A-100....and the even later MK III has the "notch " on the left hand panel to clear the magazine release button........but the MK IIs are the same except for the material as noted above by 'kacher1'..........
I'm trying to figure out your comment that YOU have noticed a "difference from the slabside,versus , any other MK II),,,,,,the "slabside" of any barrel would have nothing to do with the grip frames.