I second the notion that they are gun show magazines.

Take this with a grain of salt, my experience is based on pre-94 mags on AR15.com way back when...

Between the fact that these are curved 20-rounders and the green followers, I doubt they are pre-94. From what I understand, the green followers were adopted in the early 90s (as in around the time of the ban). So, I doubt those would have trickled into to new mag market before 1994. All of the USGI pre-94 mags I have came with aluminum followers (which work fine).

It's even more strange that you have one with a black plastic follower that doesn't appear to be "anti-tilt".