
I'm relatively sure this is a photo negative in this unopened envelope from 1929. My curiosity always makes me want to open letters like this.
Some context: this is a private collector who buys up anything Springfield related, so there is likely nothing special about this letter, sender, or recipient. Were I to ask the collector, he'll probably say to open it.
If it were a letter, I'd leave it be, but the fact it looks like a negative makes me want to open it.
Edit to add: I'm disappointed, it was a trick of light that made two squares of newspaper, not even an article, just random squares, to look like a negative. "Why negative shaped if not negative?!?!"