It is a very small market. The leading magazine is the _Celator_ (PO Box 123 Lodi, Wisconsin 53555 USA and it has fewer than 3000 subscribers in the US and around the world. They carry ads from 150 dealers in the US and around the world. This includes Greek, Roman, and Byzantine numismatics. _MOST_ collectors are interested in Roman Imperial. Only a minority collect ancient Greek coins. With such a small market, liquidity is a serious problem.