Pre-bans were made prior to the assault weapon ban of 1994. Post-bans were made DURING the ban. I'm pretty sure anything you buy new today would be called a non-ban, since even though they have the same legal status as a pre-ban, they weren't made before the ban. Post-ban weapons could only have a detachable magazine and one of the following: Folding/collapsing stock, pistol grip, flash suppressor, bayonet lug, capable of firing a muzzle mounted rifle-grenade (like WWII style, because, you know, that's a problem here in the US).
The A2 flash suppressor is both a suppressor AND a mount for some type of rifle-grenade, so it counts as two.
With minor cosmetic fixes, all the manufacturers complied and made a weapon that was still just as capable as a pre-ban. I mean come on! All that ban did was create a grey-market (sometimes black). I'm gonna be the devil's advocate and say that if you're gonna do something, don't half ass it. That ban wasn't what the anti-gun people wanted and it was a (somewhat minor, but expenisve) inconvenience for pro-gun people. Nobody got anything out of it.
I think post-ban AR's still legally have to be within the bounds of the ban. Basically, even though the ban no longer applies to newly manufactured weapons, you still legally cannot stick a 30-round p-mag in an AR that you bought in 1998 or put a nice new collapsable stock on it, etc.
< That is incorrect - please don't post what you don't know about - F>