Just wanted to put together a post with some resources identifying pre and post-ban mags. Figured it'd be good to just have them all in one place so that I don't have to keep looking and might help other people too.
https://web.archive.org/web/20090209204346/http://www.fulton-armory.com/ARMags.htm
https://web.archive.org/web/2009021...2008/10/preban-ar-15-magazine-identification/
http://www.biggerhammer.net/ar15/magazines/rawlesfaq.html
http://magfaq.tripod.com/mags1.htm
Typically brands that are good
Colt
Adventure Line
Parsons
Okay
Universal
https://web.archive.org/web/20090209204346/http://www.fulton-armory.com/ARMags.htm
https://web.archive.org/web/2009021...2008/10/preban-ar-15-magazine-identification/
http://www.biggerhammer.net/ar15/magazines/rawlesfaq.html
http://magfaq.tripod.com/mags1.htm
Typically brands that are good
Colt
Adventure Line
Parsons
Okay
Universal