[Exhibitman]

The question in many of these situations boils down to evidence: If the item was in a public collection you can be 100% certain that it did not leave the collection lawfully without full documentation of a sale. However, if the item is claimed to have been taken from the originator, like this letter, the case will turn on what evidence exists. The plumber told his son it came from a bunch of junk that Mrs. Kennedy told him he was to get rid of/could have. The Kennedy clan says no way. Since everyone is dead, however, we effectively have battling hearsay evidence issues, with perhaps none of it being admissible in court. If we never know what might have happened, no one is realistically going to be convicted.

There are also bona fide purchaser issues. In some states a thief or con man can convey clear title to a bona fide purchaser; in other states, not. It varies.

And how long is long enough before it becomes impossible to undwind? The statutes of limitations, criminal and civil, comes into play. If this item was stolen a decade ago and the person who claims it was stolen knew of the item's status, he might be prevented from reacquiring it for failure to sue soon enough to get it back and there might be no prosecution. It will depend on the state laws and where jurisdiction lies.