Sanchez began using GFs in 1989, to see if the new design would fix the feed issues. They did, and GFs were made the standard in late 1991. All USGI-contract mags made after '91 had GFs. This would include:
Okay (who also made Colt mags)
Center
Sanchez
La Belle (military mags, NOT the teflon mags)
FN
-Troy