I handled it the way that everyone here suggests that they would, I put the envelope back in the pocket and took it to the cash register, hoping that the cashier wouldn't notice it. There were no clues in the jacket or the envelope as to the identity of the owner. The jacket is vintage, at least 35 years old IMO so this could very well be something donated when the owner died. As a side note, I told my wife that when I die she should check the pockets of all my jackets before disposing of them. I have been known to keep poker money in a jacket breast pocket, inside a bank envelope in fact. My previous best find in my 4 years of thrifting was a cotton handkerchief, which is a good find IMO since I am a white handkerchief / TV fold kind of guy. Other things I have found include church programs, funeral programs, graduation programs and basketball ticket stubs. But this is the best find, $546.