Nice coin, Sherri -- You have a 20 mark gold piece from the old German State of Wurttemberg (sometimes spelled Wuerttemberg). The 10 mark pieces are the same as yours, only smaller. Here are the stats:
10 mark: 18 mm diameter, 0.115 troy ounces gold
20 mark: 22 mm diameter, 0.230 troy ounces gold
Evaluating coins like yours happens in two steps. First, you must compute the basic melt value of your coin. It is as if you took a blowtorch to the coin, melted it into a puddle of gold, and sold the puddle. (What a horrible thought to any seasoned coin collector!)
To find the melt value, go to a precious metal web site like kitco.com and find the current price of gold. Then multiply that price by the number of troy ounces in the coin. For example, suppose gold were selling at $1100 US dollars per ounce. The melt value of Sherri's 20 mark coin would be 0.230 x 1100 = $253 US dollars.
Now you must add the collector value, also known as the numismatic value, to the melt value. This gets tricky. If your coin is fully worn, stained, spotted, bent, or otherwise damaged, there is no collector value and the actual value is equal to the melt value. If your coin is fully uncirculated, bright, lustrous, and free of all cleanings and other damage, add collector values as follows:
10 mark: add $200
20 mark: add $250
NEVER CLEAN A COIN. CLEANING RUINS VALUE.
Still, we are not quite done. There are certain dates which are worth even more than the numbers shown above. Sherri's coin, dated 1897, does not qualify for lofty *good date* status, but the following coins are very scarce and qualify for large collector premiums:
10 mark 1902, 1911, 1912, 1913: add another $60
20 mark 1913, 1914: add another $2000
Yes, 1913 and 1914 20 mark coins are worth a bundle of money. Hope you have one. If you do, there are several steps you must take to ascertain and preserve value. Write to CoinQuest for more details.