[Jobu]

"... or stick them in a hot oven"

This sounds like a plausible explanation for many of the T206s out there that have one or more crispy edges/brown burn marks. I have heard rumors of a card store that had a fire (with what must have been a gigantic inventory) but many soakers forgetting about the cards in the oven for a few extra minutes seems like a better explanation for a lot of these cards.

Edited to add: Thanks for posting this David, and all of the other old hobby stuff that you post. I don't always comment but I do always enjoy reading them.