The "Art Loss Register" is a tool that may help someone track down high value, yet rare stolen coins. You have to register/sign up with them, though, and I think they're in the UK. Basically you register the coins as stolen, then if a potential buyer does a search on those coins they can determine that the coins are stolen.
Interesting how these particular coins are considered "art".
If my memory serves me, Stephen Fenton from Knightsbridge Coin may have been the person who was arrested by the Secret Service at the time of the sale of the 1933 Double Eagle that resulted in the coin being declared lawful to own.
The Art Loss Register has been responsible for tracking down a number of masterpieces looted by the Nazis that made their way to museums and private collections.
