One I took out of a Bushmaster had an "F1" mark but it was cast into the part(raised inside a recess), not stamped. I know very little about small part differences. I buy mine from Brownell's under their name and kinda trust they're not selling complete garbage(their own mags work great for me). I know there can be disparity in the price of LPK's, but I don't exactly know for what reason. My guesses are cast vs. forged, or brand name?
