After playing with some calipers I'm pretty sure they are 380 mags as the 9mm that I have ava are really short reloads. Damn the luck as I had a willing buyer for a nice price if they were 9mm.
Seems like Mark may be a willing buyer, as I read it. You know. All the posts in your thread. He even offered to help ID them at his shop. Just saying.
Spent time over at Mark's yesterday and after some experimenting; the 380 rounds fit the mags however the mags are two small for the Mac 11 mag well so the mystery continues. These may be for a early MAC 10 45 to 380 conversion, who only knows at this point.