Vintage stain

RSA95525

I have recently returned to the hobby and among my return ventures is the 1930s Batter-Up set. I was bored last night and was sifting through Ebay's listings and clicked on a card with a qualifier that I had looked at previously out of curiosity. This time I noticed something I hadn't noticed the first time I had viewed it (probably because the 'mark' was my focus). And this is something I have never noticed on a vintage card before. Of course, as a 1970s kid, I am quite familiar with staining on cards from gum. But, I had never seen this phenomenon on vintage cards. After changing my eye's focus, I noticed a 'stain' from a Diamond Stars Chewing Gum wrapper. Look closely and you can make out the words and the star where the "1 cent" price resides.

I thought this was pretty cool and wondered if I had just overlooked this on the hundreds of cards I've looked at. So I spent hours re-sifting through the listings again to see if I could find any more like this. No success. So, my question to the community is: how common is this on these old cards? I've collected for Pre-WWII cards since the 1980s and this is new to me. But, maybe others who have viewed more cars have seen it before?

I've attached pics of the card itself and the type of wrapper that may have left the stain.

RSA95525

I did notice that the wrapper I attached does not match the stain, but I haven't been able to find a photo of a wrapper that DOES match. The mystery deepens?

PaulMaul

dontippet

That is cool.