This is an official postage due stamp from the Kingdom of Württemberg, a German state that maintained its own postal system until its integration into the German Empire. Issued in the late 19th century, it features the denomination “60 Pfennig” at center within a diamond-shaped frame. The inscription “Portopflichtige Dienstsache” translates to “Official matter subject to postage,” marking it as a service stamp for government or administrative correspondence. Printed in olive green, it also bears the Württemberg state arms in the corners, adding regional distinction. These stamps are highly collectible, representing the transitional period of German state philately before full unification of postal issues.