Try #2. (Pirated wifi locked up for about thirty minutes!) Also, no heat affected zone which is a HUGE clue with welds. AND, the pin/rivet does go through, but can't get a good photo yet-need a tiny mirror. It's just hard to see after the tail end was cleaned up in the raceway. Also, a Post #6 photo shows a solder ring about the shaft of one of the rivet shanks.
Find me a bare receiver with guides and I'll happily do a cross sectional cut on the milling machine. Easy enough!
I don't disbelieve that some guides may have been welded on. I just have not seen it in person. No books, just visual inspections done over the years.