You're most likely right Ret. I was thinking mak90 was made in 1990 and had the ugly thumbhole stock for the AWB. But they weren't here in 1990 I don't think. My polytec and norinco regular stock and underfolder were bought new in 92 or 93 I believe.
On the mags, the AR ones would have followers that likely aren't as good as today. I can't remember when they went to the new style springs, but also a chance of getting the old type. Personally I never had any trouble with the old ar followers but I guess they were improved for a reason.