Not 100% sure, but my understanding of the 1990 Donruss cards is that almost all of the cards can be found with three variations. The dot (Inc.) and no dot (Inc ) were in packs, probably because of multiple printers being used.
The factory sets all have the dot (Inc.), but have a different splatter pattern on the front of the cards.
I haven't found any 1990 variations harder than the others.
Here are the three different Cal Ripken Jr cards (3rd one is from factory set)
SCAN9579.JPG
SCAN9580.JPG SCAN9580-1.jpg
FYI - Donruss BB sets from 1987-1992 all have multiple variations. The 1989 Donruss set have cards with as many as six different backs.