Is there such thing as a "missing coin"?(st. gaudens)?

It is not a coin but a 3" or so replica. I have one also and I got mine at Saint Gaudens studio here in New Hampshire. His studio is less than 1 1/2 hour drive my house. it is run by the nation Park service. It is a copy of the high relief Roman numerals version. These large medals, they are really not a coin, have been around for many years. It is gold colored and not real gold. I also have one that has an 1877 Indian head cent on it. That is the rarest Indian cent. It to is 3-4 inches in diameter. The Indian goes back to the 1940's, for it has been in the family since then. They have very little value and can be bought still at the studio.