Sandra, congratulations! If your coin is genuine, it is very valuable.
These coins were minted in gold under the rule of Franz I, emperor of Austria (FRANCISCVS I AVSTRIAE IMPERATOR). There are two denominations, the ducat and the 4 ducat. They are similar, but the 4 ducat is, predictably, four times heavier.
The base value of these coins is determined by their gold content. Use a website like kitco.com to find the current price of gold.
1 DUCAT: 3.4908 grams - 0.1107 troy ounces of gold.
At $1470 US dollars per troy ounce of gold, each ducat has a base value (BV) of $1470 x 0.1107 = $160 BV
4 DUCAT: 14 grams - 0.4438 troy ounces of gold.
$1470 x 0.4438 = $650 BV
Below are given are very approximate catalog values for these coins. They are exceedingly rare, and whenever a coin is sold, it stands on its own merits. Coins with attractive eye appeal are worth much more than coins with a tainted eye appeal, even if there is similar wear on the coins.
worn: BV + $10 US dollars approximate catalog value
average circulated: BV + $40
well preserved: BV + $80
fully uncirculated (like our picture): BV + $150
1 ducat coins dated 1812G, 1813G or 1814G (must have G mint mark) are so rare that the catalogs don't even report their value.
1 ducat coins dated 1815G are slightly rare and worth a premium of approximately $40 on top of the values quoted for common dates above.
worn: BV + $100 US dollars approximate catalog value
average circulated: BV + $350
well preserved: BV + $1300
fully uncirculated (like our picture): BV + $2000
Values are similar for all dates in the 4 ducat series.
Remember that these are inflated catalog values and only apply to coins free of problems like cleanings, gouges or damage from jewelry mounting. Please read our 'Important Terminology' page on the top left to properly understand what these catalog values mean.
CoinQuest thanks Heritage Auctions for use of their coin photo. It is a beauty.