Family made a serious mistake when it handed over the coins for authentication. No doubt the offer to authenticate was a ruse.
Possession is 9/10th of the law and the family is most likely SOL.
especially considering the dead guy was a jewler.
How does the family NOT trust a guy who was probably a metals expert ?
Posession might be nine points of the law, but the only reason I can think of, they wanted to initiate a process by which they will become the legal owners of the coins. Sounds like a stretch, but as contraband they could only have sold them on the black market. If they become "legal" again they can be sold and resold and public auction.