Actually, it's unclear whether the king or the coin dealer was in possession of that single coin. (Not that it matters.)
What's the difference now?
The government has not relinquished its rights to these 10 coins (there hasn't yet been a "legal battle" such as the one that resulted in that sale). If Langbord can hire the right lawyers, she might have a chance.
Again, if these 10 were originally obtained illegally, I'm thinking seizure is justified. If your lawyers can negotiate a deal, more power to you (and money to them, obviously).
You both definitely have a point that the coins were stolen property and taking it back is what the government does with stolen property. I still think the disparity between King Farouk's (or whoever's) coin and these coins is unfair.
I guess the thing that really kicks me in the gut is that they handed them over to the Mint or announced even that they had them. I wonder, because they couldn't be so ignorant of what these coins represented, if maybe they've got 20 more back at the jewelry store.