Vern,
Some observations:
The receiver in front of the sideplate does show use wear (pointed out in the photo) although it is indeed very light. In my experience this wear pattern varys with the fit of the parts, and does not necessarily wear through to the steel.
The breechblock does not at any time contact the flat portion of the frame ahead of the holdopen. Although the photo is not conclusive, it does not appear that the steel at the bottom of the breechblock is worn. Also, note that the wear mark on the flat is matched by a wear mark on the angled relief cut in back of the holdopen (arrows); these marks are characteristic of the end of the recoil spring stirrup connector dragging across the frame during disassembly/reassembly.
What is your assessment of what appears (to me) to be very clear patina (rust!) in the unit mark stampings?
--Dwight