Stan;
I am in total concurrence with your thoughts that most guns come "Off Face" through wear & not from actual shooting. I cannot really see how a hinge joint would wear one-sided. fro opening & closing. Further the way you described you treated this gun it should have little wear. .
To go off face from Shooting, then it would certainly seem to me that metal had to either Stretch, Compress or Bend, depending upon the location.
As I recall this is a double under bolted gun, have you noticed any signs of Rub Marks on either side of the rear lump..

Miller/TN
I Didn't Say Everything I Said, Yogi Berra