There is a German coin with King Otto on it. It would say, "Otto Koenig Von Bayern."The reverse side would be a bird with wings spread out. Does that sound the same? It would be clearly marked, "Deutsches Reich", and a date followed by it's value, probably , "20 Mark". If that matches, it's worth about $450-475 if it's uncirculated and in a protective holder. The value would go down from there based upon it's condition.