The half franc in our picture comes from Poinsignon Numismatique in Strasbourg, France, where it is on sale for 700 euros, about $920 US dollars. The coin is in great shape, and this is the primary reason it commands such a high price. Coins in more crude condition would not be worth this much.
Henri IV ruled France between 1589 and 1610. Many different denominations of coins were produced, but only the 1/4 and 1/2 francs use the four fleurs-de-lis pattern on the reverse.
These are valuable coins. Condition makes the biggest difference, not date or other details. Catalog values run like this:
worn: $100 US dollars approximate catalog value
average circulated: $500
well preserved: $1000
Damage to the coin, such as cleaning, scratches, gouges, and the like lowers value substantially.
CoinQuest thanks Poinsignon Numismatique for use of their coin image.