What you may be encountering, and it's not easy to say without having that pistol on my bench, is a slight twist off location of the grip frame lug and the receptacle for the lug in the bottom of the receiver. The early 22/45 pistols did not have the lug receptacle swaged, or peened down to arrest any possible rotation of the upper on that grip frame lug, like so:
It would not be all that difficult to rotate that upper so it's more closely centered into the grip frame, but you'd need to remove the mainspring housing assembly and the bolt to get that done.
That "knurling" on the muzzle end is interesting. Kinda wonder if the muzzle end was threaded for a compensator or a suppressor.