I’m not going to guess at metallurgy, but I just compared a brand new USA mag to an Italian one that has about 250 rounds through it, and the finishes look the same as the ones in the photos above. The USA-made Checkmate had more rough-looking holes punched in the metal, has sort of a burr at the base in the rear, and has the same kind of pebbly finish as the one in these photos. I’ll post my own comparison photos when I have a chance.
Having said that, I’ll reserve judgement on how the USA mags perform until I’ve put a couple hundred rounds through them. Up til now, I’ve been using Italian SIG factory mags and ACT mags, because that’s all I had. I really don’t expect the US-made mags to perform much differently. Like many products in this industry, a manufacturer may produce different levels of quality for different customers based on their specifications.