I have 2 warnings -
Rich Muchin - I bought 2 books from him on separate occasions at shows about 10 years ago. Sgt. Fury 1 and Hulk 6. Years later, my more knowledgable eyes have detected that both books are restored with color touches and tear seals. The Hulk 6 is a very sharp 7.0 - 7.5, so I sent it to Matt Wilson to see if he could remove the resto so I could get a blue label. Unfortunately, because it was amateur touches, he could not remove the color touches. Of course, no restoration was disclosed at the time of purchase.
Samco1 - I recently bought a few books from him on ebay. Out of 2 books, one book had color touches (a $25 TTA). He accepted a return with no problem, then found another comparable copy and sent me that as a replacement. I can't tell for certain, but I strongly suspect there is a small color touch on this comic as well. Too bad, because it's a gorgeous glossy VF+ otherwise. Not really worth sending to CGC to find out for sure.