The coins were never released into circulation, so they were stolen from the mint.
I'm not sure I have much sympathy for the family, and I sure don't have much respect for their intelligence in giving them to the mint to verify authenticity.
After so long a period of time they have commited no crime nor are guilty of no crime.
So, I think the mint actually has no claim to the coins whatsoever.
And that is why they caved before and will probley do so again.
They wouldn't be "among the most valuable coins" if there weren't SOME in circulation.
Hard to fault them for their intelligence. By getting them authenticated, and then raising a fuss, they were able to get ONE coin auctioned and it made them almost 4 million dollars, LEGALLY, without ever having to worry about getting caught.
Not bad for stolen property. I think they aren't as stupid as it seems.