M1 carbine magazine questions

I am helping my Aunt sort through some of my Grandpas things so I am starting with the M1 carbine magazines. I have read through most of the threads on this topic, however I m having a hard time trying to figure out exactly what I have. Not in the sense of who made them, but if they are USGI, Korean, ect. I am hoping you guys can give me a hand.

The following are magazines that I have that I am trying to get straight. So would I be correct with the following?
30rd split back that is stamped M2; not USGI, Knockoff, low value
30rd split back that is stamped SEY; USGI
30rd hard back that is stamped SEY; USGI

I am also sorting many 15rd some are AI, U, PMC, IA, I think RUGG, KC, SW and a few others. Im lucky that my Aunt is letting me keep a few. I can post pictures in the next day or so if that will help.

Thanks for all your help!

You are likely correct on the 30s, although it is possible that the splitback SEY could be an aftermarket. Without seeing it we can't tell. The PMC is, I believe, a Plainfield Machine Co. mag.

You might also note the 15 round GI magazines where the front fold/seam is to the right and those codes that fold to the left. This can be seen while looking down on the follower with the fold facing forward.

Chuck