Nice coin, Helene -- To find the value of your old 20 franc coin from France, first compute its base value due to gold content. Look up the value of gold per Troy ounce on a web site such as
kitco.com. Then multiply that value by the amount of gold in your coin. In the case of a Napoleon 20 franc coin, that is 0.1867 Troy ounces.
For instance, at the moment gold is running $1105 US dollars per Troy ounce. Tomorrow it will be different, so be sure to look it up. The base value of your coin is then 0.1867 x 1105 = $206.
A worn or damaged coin will be worth the gold content alone. A coin in excellent condition will be worth $100 more (or even more), which, in our example is $306.
Since Helene indicates her coin has little or no wear and sports attractive eye appeal, the retail value is probably near the $300 mark. Selling it to a coin dealer would probably bring $50 to $100 less than retail. The mark-up keeps the dealership afloat.
All the dates and mint marks in this series of coins are worth about the same amount, as cited above. An 1856D coin has a low mintage, so it might be worth a little more.
