Another dumb question, would chemical exposure affect the back, too? I'd think so.
The back might be the cleanest of any of the 40+ T206s I own. I'd suspect I'd see something there, too, but, it's clean as a whistle.
It really is striking how different this seems to be vs. "regular" versions of the card. The yellow is completely gone from mine it seems.
Example of a normal version:
