I read about the magazine stud here: http://www.milsurps.com/showthread.php?t=17575
It is a pretty interesting thread.
The 23 thing is interesting, and it does seem to be a PITA to do...the why is confusing too...it isn't like you would think anything but the whole mag would be replaced...perhaps they weren't sure about what would be a refurbable portion at that point yet. Maybe there was a little more personal fitting going on in the beginning. It seems unlikely that it was done at refurb, if anything...it may have been done pre-assembly for some reason. If it is a coincidence, it is kind of over the moon. I really would like to see if anyone else can see it perhaps under the paint...I really wasn't looking for numbers there...and the paint was on thick. There still was plenty of scrubbing after I discovered the numbers...I didn't see the follower mark until a considerable time scrubbing away at the body. Unless someone has gone to the trouble of doing what I have done, it is doubtful anyone has noticed. I suspect the early mags like this that escaped the paint are few and far between. It may be visible to someone not already halfway done scraping it clean though...it is in probably the filthiest spot on even the cleanest gun. It's like a very deep naval in there.
Whatever gun this came from must have been a beauty, the mag is seriously as new as new can be underneath the paint. It didn't exhibit any of the metal treatment I saw on other parts during stripping...it may have been stamped and painted in the white. All the other refurbed parts had kind of a dull park like finish to the metal, I assume some kind of etching process for roughing up the metal for better adhesion. It is pretty thin and steel wool makes quick removal of it....unless you do a chemical plating reaction with the acid and a brass brush...which turns it golden.
I think that might be the mystery of the golden bayonet, (also discussed in that link) if during the finishing process they used an acid along with brass brushes, this effect could be caused by something as simple as that....perhaps usually they used steel brushes, and substituted out brass...ran a run of bayonets through it, some even getting final polishing before the error is noticed. This metal prep process used before painting could be also a same/similar process before chroming the bayonets...later matte bayonets might have just had the chroming process skipped....
All speculation that came about from doing all of this by hand, and never quite duplicating the process...I did eliminate the part where each part turned gold, by either using paint stripper exclusively with the brass...no goldening, with acid and steel, no goldening....acid and brass, it looked like I electroplated it with iron pyrite if that is even possible. I had thought that perhaps first came the grey layer, and then the golden...but by eliminating brass, I think I put that to rest. The bayonets might just have been experimental and that was why so many small variants exist. I don't believe the soaked in cosmoline theory at all. This one seems more likely. Whether it was on purpose or just an anomally remains to be determined.