Re: Statue Of Limitations Question
I would think that if you found the proceeds of a Bank Robbery, it would forever belong to that bank, or their successor's-in-business, indefinately. Heck, wasn't there even some insurance company's trying to get at the Brother Jonathan's 1850s shipwreck gold, because they claimed that they, by succession of insurance companies that had been bought & sold, 50, 100 or 150 yrs. earlier, they could trace a claim through the tree/evolution of mergers, etc...?
Or how about the true story of some kids who found a cache of very old money in the dirt floor of their rental house in NY years ago? By the time that was over, there were multiple claimants all saying "it was mine, I left it there" etc... Property managers, current and previous owners, the renters themselves, past renters who had rented that unit years earlier ("yeah! that's the ticket! I buried my antique coin and bills collection and forgot it when I moved out!"). So even the age of $$ can be a non-issue, since someone can claim they were a coin collector, etc..
Best bet, when you're certain it's something that goes way back before modern times, and has long been given up on, is to remain quiet. Now if you found something you reasonably expected is a current loss (a diamond ring in a parking lot with an insurance name on the inside), then of course, you can't hawk it and expect to walk clean. These are just recommendations, of course, I suppose if we all wanted to be technical enough, we should even seek to return that lost (or stolen) barber dime we found at 8" in the turf a the park, right? The rightful heir are still out there somewhere, or the kid who buried it the day before, so you only think it was a loss in older times. Etc.. Etc....
There's also legal statues about the value something, that varies from locale to locale. Like, if it's worth $50 or more, you are expected to turn it into the police or something.