Wurttemberg was a kingdom in what is now Germany. Like many areas in Germany, private railway stamps were issued, in this case inscribed Wurttemberg Staatsbahnen
(Staatsbahnen is essentially translated as "State Railway"). Scott has not gotten around to adding these to the Scott Classic
Here is an assortment, from pfennig through mark values:
I am not showing an express value. If someone has one to show, please add it.