Mac 10 in 45acp, 11 in 9mm and 12's in 380 were made by Military Armament Corp hence MAC name. They used steel mags.
S.W. Daniel under the Cobray name made the m11/9 and m12/380 that used plastic mags.
2 different groups of people.
They look similar to a m11 from cobray, however the m11 steel mags had a wrap around steel piece on the top half to encompass the feed lips. The May be from a Mac 10 hybridized to fit 9mm or something like that. More familiar with the m11 than the 10, hope it helps.
Just an observation, but mccullma offered to take them all in the post above. Seems strange you would be listing of GB, but maybe something was discussed behind the scenes? just saying, carry on.
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.