Orig mfgr's
Vince, real G I issue mags.........USUALLY are the brand named "BRW"...........this is the most common NOW.
And is the one Springfield used to ship with their rifles.........
ALL, the Chinee's, are UNmarked, and are sometimes wrapped in wax paper, and greased.
Another American mfgr, is marked C I , they are good also..........any others, I would steer clear of.......especially f they are over $30-40..........
The Chinee's work well.........IF, and a big IF, they will fit into the mag well, and lock into place.
PS: the only markings are found "Stamped", into the back of the mag, about an 1-1/2 up from the bottom.............if there are NO markings.....then they are not ISSUE mags.......unless they have been refinished, and sandblasted.