The Alsace-Lorraine (in German: Elsaß-Lothringen) was a territory created by the German empire in 1871, after the annexation of most of the Alsace and the Moselle region of the Lorraine in the Franco-Prussian War as part of the Treaty of Frankfurt. French troops entered the Alsace-Lorraine in November 1918 at the end of World War I, with the territory reverting back to France under the Treaty of Versailles in 1919.
In 1870, at the beginning of the German annexation, a set of postage stamps was issued for the Alsace-Lorraine. But on January 1, 1872, these stamps were replaced by stamps of the German empire.
However revenue stamps for the Alsace-Lorraine continued to be issued throughout the annexation, including those to tax railway carriage of goods contracts (in French: Lettres de Voitures).
Of particular interest for Luxembourgian philately are the four revenue stamps issued in 1903 for use in connection with goods transported on the branch railway line [or Nebenbahn] from Diedenhofen (today: Thionville) in the Alsace to Mondorf-les-Bains in Luxembourg. They are shown below:
The design is the same as that used for the main German railway in the territory -- the Reichs-Eisenbahnen in Elsass-Lothringen. The text reads:
The stamps are typically found perforated on some sides and rouletted on others. The Yvert & Tellier Catalogue des Timbres Fiscaux et Socio-Postaux de France says the stamps rouletted on all four sides are scarce.
Similar revenue stamps were issued in 1905 for the branch line connecting the Alsatian towns of Rosheim and St. Nabor.
Who has seen examples on documents? Canceled examples of the 30 Pf. and 40 Pf. and a 1915 Frachtbrief from the line can be seen on this wonderful website: http://www.rail.lu/lignesfr/lignethionvillemondorf.html
Your Luxembourg railway cancel collection won't be complete without the Diedenhofen-Mondorf railway cancel on a loose stamp or document!