The picture shows a 2 reichsmark piece from the Weimar Republic. The Wiemar Republic existed in Germany between the time of the old German Empire and Hitler's Third Reich.
Catalog values for a most dates of a 2 reichsmark coin run like this:
worn: $10 US dollars approximate catalog value
average circulated: $25
well preserved: $45
fully uncirculated: $110
You have to be careful about catalog values, though. They tend to be inflated. Please look at the Important Terminology page to get a feel for what you could actually sell the coin for.
Some dates of this coin are worth more than the nominal values quoted above. These 'beter dates and mint marks' are called out below, with an approximate catalog value for a coin in well preserved condition.
Thanks to cgb numismatic for use of their coin image. It is a beauty!
The gold toning that Gus mentions is generally desirable. Other tonings, such as grey and brown, generally decrease value. Gold toning leaves it the same or, in rare cases, raises value.