Marking your coins
If you are in the U.S. and are planning on making close copies of actual coins, you will need to comply with the Hobby Protection Act of 1973. This requires the word COPY to be incised into each coin you make to show that it is a reproduction. If you want to avoid this, you can try doing things like altering the legends your coins, having the ruler's bust face in the opposite direction, change the devices in a coat of arms, anything that would make it an obvious fantasy yet still look realistic. I made a copy stamp that fits the specs for the law and use it on coins from my pine tree shilling dies but on fantasy pieces, I don't worry about it.