Thanks. I also read this:
"Refinished magazines: As the supply of M14 magazines on the civilian market has dried up since the September 1994 ban, many dealers have turned to re-phosphating any worn-looking magazines to keep up their inventories. The quality of this work varies, but in general, if they start with the original U.S.G.I. article, the end result is a good functional magazine. (But once re-finished they of course have little or no collector's value.) In recent years Springfield Armory has refinished thousands of G.I. magazines. Some of them look a bit nasty, since the magazines show pitting beneath the re-phosphating. The supply of M14 magazines is currently so scarce that Springfield sell their re-finished magazines for more than $50 each!"
These mags are the dark dark grey (almost black) parkerizing, and didn't come in packages or in grease. The quality of construction is consistent (along with cosmetic appearance of welds) with USGI mags I have marked BRW, UHC, and W (which, according to Different's sources, is Westinghouse, not Winchester). The markings aren't there.
I was curious about SAI either removing markings since I recently got an AR10 from ArmaLite. Since ArmaLite hasn't released their new redesigned mags yet, all of mine are clearly M14 mags that were converted (shortened feed lips, new follower with plunger, new base plate with logo, and AR10 mag catch slot cut out of left side). Instead of seeing makers marks of the original bodies on the back, I instead see where it looks like it was taken to a grinder, and a new stamp that says "US Patent X,XXX,XXX" in its place.