1968 Topps Baseball, Altered?
 

I recently purchased a box containing over 100 1968 raw baseball. I noticed that several of the cards had these brown diagonal lines on the back. Some throughout the whole back others just random. Only on the back. Does anyone have any ideas what these are or what created them ? I’m guessing that the cards were altered in some fashion hopefully not counterfeit. Any ideas? Thanks

I’m guessing they were removed from a photo album and that is residue from the sticky adhesive.

I could see that. There were a few cards with paper loss as well.thanks

definitely album adhesive.