Billy Yes the "stains" on the back are intentional to give it a more "vintage" look. Sadly the "stains" were exactly the same for each card. I don't think they did any ranomization in the location, size or shape of the stains. Some cards seem to have it lighter or darker. That might just be regular inking issues.
I collect: Baseball, Football, Hockey, Mostly Vintage pre1980, My Homie teams - Washington/Baltimore Teams Senators (Twins, Rangers), Expos/Nationals, Redskins, Capitals, Bullets/Wizards - HOFers - Non-sport (mostly TV shows and movies).
My Trade List is very much a work in progress
CaptKirk42s Trading Card Blog Curly W Cards Strive For '65 YouTube klandersen42