Kingdom of Württemberg Bahnpost (DE)
From Stamps of the World
The Royal Württemberg State Railways (Königlich Württembergische Staats-Eisenbahnen or K.W.St.E.) were the state railways of the Kingdom of Württemberg (from 1918 the People's State of Württemberg) between 1843 and 1920.
Stuttgart (St)
St in cancel and a clerk/employee number for each cancel.