1990 Donruss Proofs?
 

Anyone know if these are legit? Seller says they are printed on thin paper and they seem similar to the 1990 Donruss Blue/White but these are blank back.

Here is an auction that features some of these, with a description of the type in your picture:
https://www.robertedwardauctions.com...rd-collection/

While I can see the potential for someone wanting to fake a proof from 1990 Donruss (especially the examples of proofs that exist for cards that didn't make it into the final set) I would have some doubts someone would go to the effort to fake a Keith Miller card... Then again, stranger things have happened!

I would be suspicious of that one. Too many things that there's no reason for them to be in Blue are there.

That being said, it's also possible there were things that were being tried out. I don't know how much proofing Donruss did, but if it's anywhere near what Topps did it's entirely plausible.

Here are some from Donruss from around that time:
https://www.comc.com/Cards,sc,=Donru...+Boggs,ot,i100

Yes. I'm no experts on these cards, but, for a color progression proof, only the blue parts should be blue. I don't know why the red parts of the card would be blue.

Fleer did a couple of mail-in posters in blue like that for their Stamps and Stickers. I believe the idea was that you'd order the parge poster and then stick your stamps/stickers on the poster in the right spot, like the albums.

Some of those have been cut apart and sold as proofs, but they are simply a poster cut.

http://1978theyearitallbegan.blogspo...ps-poster.html

http://1978theyearitallbegan.blogspo...r-sticker.html

Not saying those Donruss are not some sort of proof, but this is very similar. I grabbed one of the 90 Donruss "proofs" from ebay recently myself. Same seller had some 82 Donruss that were also blue. They were cheap enough to not worry if they do turn out to be fake, but this guy had a lot of proof cards too.

The seller is a member here and Ive bought quite a few proofs, blank backs, etc from him.

I am pretty sure you are talking about ebay seller shoeheart. I have bought from him as well. If those are not legit Donruss issues, I suspect he is probably not aware of it as I have no reason to question any of his listings.