There have been several recent blog posts about late 80's / early 90's era variations and those that strive for them. I count myself as one of them. I didn't actively collect between 1985 and 2003, so I missed the whole junk wax era, but I do enjoy seeking out those subtle variations in everything from Pro Set football and hockey, to 1980s Donruss and Fleer, through the early Upper Deck years, and beyond. I've spent whole afternoons squinting for incomplete stat lines and misspellings and considered it time well spent.
The latest chapter in my quest comes from a trade I recently made for a set of 1990 Upper Deck. Believe it or not, it's 2017, and there is a set collector that didn't have 1990 Upper Deck. (Still don't have '89, but that's for later).
The major errors in that set come at #101 through 199. The copyright line that appears on the back underneath the MLB and MLBPA logos is missing on all 99 cards.
These variations don't appear to be very rare, so they should be found in most every bulk box of 1990 UD you find. This is the appeal of the variation hunt to me. They're cheap and easy to find, but still interesting.
I don't have these posted on my want lists, but I printed out a list that also includes the other variations in this set, most of which occur in the high 500's and up. Go here for a complete list. There are a lot of UERs that don't count listed there too. I would post my wants here, but I still have several that I need the "line present" version etc., so it's a bit cumbersome. I'll wait until I've had the chance to dig through a few bulk boxes at shops or shows and then put up what's left.