Fantastic coin, Todd. If your coin measures 38 mm in diameter, or about that, you have an old thaler from Austria. A smaller coin would be a half thaler. These big silver coins are well sought by collectors.
The coin in the picture is from Coin House SESAM Basel and is on sale for about $100 US dollars. If yours is in worse shape, with more wear and scratches, value will come down from there. In better shape, the value would easily reach several $100. If you are selling one, figure that dealers would pay about one-half of these retail values.
Two caveats apply to all valuable coins:
1. NEVER CLEAN A COIN. CLEANING RUINS VALUE.
2. Be aware that counterfeits abound. Don't buy from untrusted sources.
The coin in the picture is typical for this series of thaler. There are a several rare dates and mint marks:
1806A - extremely rare
1809B - $500 when average circulated
1812A and C - $350 when average circulated
1813C - $350 average circulated
1814B - extremely rare
1819B - extremely rare
1820B - extremely rare
1822V - $700 when average circulated
1824A and C - extremely rare
1827B - $300 average circulated
1833A with 'FUNDAMENIVM' on the edge: $200 average circulated
1833B: $750 average circulated
1831A coins are interesting. If the ribbon on the emperor's wreath goes forward across his neck, the coins are common and catalog at the usual values.
However, if the ribbon hangs down behind the emperor's net, the 1831A thaler catalogs at $800 when average circulated.
These little differences are what get collector juices flowing!
CoinQuest thanks SESAM Basel for the use of their coin image.