sammler.com, a major German collectibles site, lists values as of 11/2011 as:
Moderately worn: US$16
Slightly worn: $21
Uncirculated: $35
The German wording translates as Wilhelm the Second, Kaiser of Germany and King of Prussia.
You are asking about a 10 mark coin from the German state of Prussia (KM#504). The coin weighs 3.982 grams and is 90% gold, giving it an AGW (Actual Gold Weight) of 0.1152 troy ounces. With gold priced at US$1,536 per troy ounce (as of June 2, 2011) the "melt" value of the coin is about US$177.
The front of the coin bears an image of Wilhelm the First and the words "WILHELM DEUTSCHES KAISER KÖNIG V. PREUSSEN" (German for "Wilhelm, German Kaiser (or Emperor), King of Prussia"). There is also a small "A" beneath the portrait, signifying that the coin was minted in Berlin. The back has the shield of the German Reich (a shield on the breast of a stylized crowned eagle) with the words "DEUTSCHES REICH" (German for "German Empire") and the date ("1880") above, and the denomination ("10 Mark") below. 1,762,000 such coins were produced in Berlin in 1880, the second most common mintage in the series (which ran from 1874 to 1888 in Berlin, and for shorter periods at the Bayreuth and Cleve mints).
According to the Standard Catalog of World Coins, the coin is not worth much more than "melt" value in circulated condition, perhaps US$250 in Uncirculated condition and US$325 or so in Brilliant Uncirculated condition.
It is worth much the same as the English sovereign and its value increases depending non the letter under the head and "A" is the most expensive.
In average condition, it retails for about $30. If it has only a slight amount of wear that figure jumps to about $150. Your coin is from Prussia, one of the German states that continued to issue its own coins after the 1871 unification of Germany. The "A" mint mark indicates it was minted in Berlin. Prussia's head of state, Wilhelm II, was also the Kaiser (king = "konig" in German) of the united German Empire (= "Deutsches Reich")
Yes there is 50 mark coin from 1878 with Wilhelm the 2th Deutsche Kaiser Konig V.Preussen on it .
Kaiser Wilhelm's grandmother was Queen Victoria of England.
Kaiser-Wilhelm-Universität was created in 1872.
Kaiser Wilhelm Bridge was created in 1907.
The cast of Kaiser Wilhelm II - 1914 includes: Kaiser Wilhelm II as himself
The cast of Kaiser Wilhelm at Stettin - 1902 includes: Kaiser Wilhelm II as himself
The cast of Kaiser Wilhelm in Hannover am 19.12.1903 - 1904 includes: Kaiser Wilhelm II as himself
The cast of Arrival of Kaiser Wilhelm in England - 1903 includes: Kaiser Wilhelm II as himself
The cast of Kaiser Wilhelm Inspecting His Soldiers - 1902 includes: Kaiser Wilhelm II as himself
The cast of Queen Wilhelmina and Kaiser Wilhelm Riding in the Tier Garten - 1902 includes: Kaiser Wilhelm II as himself Queen Wilhelmina as herself
Kaiser wilhelm II was 5 foot and 7 inches