Below is something I posted on another forum about the possibility of another vintage football set with a color variation, and the reason for me looking for lots of this set to help with my research.
I've spent a little time exploring the possibility that there may be a 'purple sky' variation to the 1964 Philadelphia cards. I first noticed this when I found a really nice Amos Marsh card to upgrade the one I had. Of the five Cowboys in this set that I've noticed something odd with the background, the Marsh is the most obvious. I've talked about the 1963 Topps purple sky variation a few times before, and the variation in that set is documented in Beckett. Beckett doesn't say anything about the '64 Philly set having any variation.
I've picked up a few more Cowboys cards in this set in the last few months to try and further explore this theory. Pictured below are the side-by-side comparisons of the cards I can see more prominent red pixels on. Unfortunately, the scanner doesn't help my cause here very much because it doesn't pick up the difference as well as it can be seen in person.
Even the white background of the Team Play Card has a pink hue to it. Notice how the right edge of the top card blends in with the back of the scanner bed, and the bottom card displays a slightly different color that allows you to see where the card ends and the scanner bed begins.
This interests me enough to start looking for cheap lots of 64's on eBay to try and find if this occurs with other cards in the set besides the Cowboys. This may not interest many of you guys, but my wife could care less, so I need to get this off my chest somewhere
. I'll post an update after I gather more cards.