I`ll have to check that out. I don`t recall seeing the stamp. But i`ll check this weekend...It`s in the safe in the basement, I don`t feel well, and I have to be out early tomorrow for an out of town meeting.Your Colt "factory" mags may very well be Metalforms. Now that I think about it, the two Colt marked mags that came with my Super are Metalforms (small "M" stamped in the corner of the baseplate). All work perfectly!