You can either choose to sell the coin on eBay or through a specialist like. It will give you an idea of the amount of money that the coin is going for. Search the full name of the coin, select the 'sold' listing and then toggle the search to 'highest value'. You should check how much the coin is selling for on eBay.
These are often deemed the most valuable by collectors. The most valuable coins are usually those with a low mintage or an error. IF you think that you might have a rare coin then you might be able to make a real mint.
