Regarding the secret compartment, I first saw a coin like this at the CIA Museum that had supposedly been taken from a Soviet spy. I think I've seen coins like it in spy books but it is too early in the morning to try and find one of them on my shelves. Any thing about them has always said they were used for hiding microfilm. I always wondered how they made them.

These may be part of a wartime spying gimmick. There have been lots of hollow coins made; perhaps electroplating is easier and less time consuming if making several copies. Messages go inside, along with a stiffening piece that fits. If it looked and felt right, the walker wouldn't attract suspicion. I'll be interested to learn the real story on this item.

I have several half dollars like this, which seem to be magician's coins. Two half dollars are used. The first is machined down to encase another coin (usually a British coin like the one pictured previously, or a Mexican 20 centavo). Another half is machined down to fit into the obverse shell. The "solder" is likely the adhesive used to attach the foreign coin to the interior of the half dollar shell. I find these in circulation all the time when I search $1000 bags of halves from the bank. Last week I found two- half dollars dated 1976 and 1996-- in the same bag. The interior of the obverse shell on my coins has the same markings are the coin pictured in the article.