Look at this gorgeous Prussian thaler currently one sale at Manfred Olding for an excellent price of 185 euros (about $240 US dollars). You can see every hair on King Friedrich Wilhelm's head and the color and overall appeal of the coin are very pleasing. If your coin looks like this one, Erica, the retail value corresponds to Manfred Olding's. With more wear, the retail value will go down to $100 or so. If you wanted to sell your $100 coin to a dealer, he or she would probably pay about $50 for it. The markup keeps the dealer in business.
Here is what the catalogs say about this series of old thalers (pronounced like 'dollar' but with a 't'):
Coins with A mint mark: $100 in average circulated condition rising to $450 in fully uncirculated condition
Coins with D mint mark before 1828: $200 in average circulated condition rising to $1500 in fully uncirculated condition
Coins with D mint mark after 1827: Same as coins with A mint mark
Coins dated 1827A and 1828D: $300 in average circulated condition rising to $2000 in fully uncirculated
The A coins dated 1823, 1824 and 1825 are slightly more common, and they catalog around $50 in average circulated.
Be sure you check the meaning of 'catalog value' at our Important Terminology page. You may be surprised what it says.
NEVER CLEAN A COIN. CLEANING RUINS VALUE.
While Manfred Olding's thaler is a beautiful piece, compare it to another example of the same coin currently on sale on eBay by a dealer we will not name. The eBay coin has been worn by circulation and then cleaned to make it look 'new.' Any discerning eye can tell that it is not new! In fact, the cleaning has rendered this coin essentially valueless.