Right.  For example: let's say you bought a Colt Sporter with pistol grip and flash suppressor, but no bayo lug or collapsable stock, back in '92.  This gun accepts detachable magazines, and has TWO evil features, which qualifies it as an AW, and allowed it to be grandfathered as such.  There is no problem with adding additional evil features to this rifle, as it is already a grandfathered (i.e., legal pre-ban) AW.

Now, if, back in '92, you had bought some custom AR15 with no FS, bayo lug, grenade launcher, or collapsable stock, but JUST the pistol grip (one evil item), that rifle would not have had enough features to be classified as an AW.  Even though this rifle was a complete rifle before the ban, it wasn't a complete *assault weapon* before the ban.  Of course, if you had owned the gun the entire time, you could make a case that you had, at some point, put a seperate upper on your lower that WAS in AW configuration, which would have been enough to qualify.

Where this second situation gets people is with guns like the M1 Carbine, Mini-14, or 10/22.  Few of these guns came with enough evil features to have qualified as AWs, so even if they were *manufactured* before the ban, they are most likely "post-ban."  Models like the Mini-14 GB, which came with folding pistol-grip stock, FS/grenade launcher, and bayo lug, obviously DO qualify as pre-bans, as they had plenty of evil features.  Same with the M1 Carbines with the paratrooper stock.

Hypothetically, if you owned, say, a standard Mini-14 since before the ban, it would be very difficult to prove that you had never, at some point before the ban, added enough features to qualify as an AW.  Having had the gun since before the ban (and from before any of this crap mattered), you wouldn't have a problem creating reasonable doubt in court.

On the other hand, if you bought the same gun AFTER the ban on a 4473, and you have nothing from the original owner to vouch for the gun's pre-ban status, I would suggest that the gun NOT be configured to AW configuration, as creating reasonable doubt would be much more difficult.  BATF could in most cases trace the gun and show you purchased it after the ban, and without any evidence to submit on your behalf (and heresay isn't admittable), you'd have a tough time.

Last: remember that the above only concerned DOMESTIC guns which must follow the 1994 Krime Bill; imports must ALSO abide by the 89 Import Ban, which is why guns like the SKS are so hard to figure out.

-Troy