1872, Letter in "double Franco-German port" from Haguenau (Alsace Lorraine) to Paris, franked at 2 groschen with Brustschild Mi-Nr. 5 stamp cancelled "Haguenau / Elsass / 1.1.72" on the 1st day of issue of the German stamps corresponding to the port in German territory, then 25c tax in blue affixed in Paris for the French part (corresponding to the domestic tariff of 1st September 1871). 5 known letters in mixed postage cancelled on the first day of issue and only 3 with the French tax, a major piece of postal history of the 1870 war. Very fine quality piece and certainly one of the finest known, certificates Hennies BPP (1980) and Brugger BPP (2006): "von den fünf registrierten deutsch/französischen Doppelfrankaturen mit Brustschildmarken vom Ersttag der Brustschilausgaben weisen drei die vorliegende Portodarstellung auf. Die wenigen Auslandsbriefe gehören zu den interessantesten Ersttagsverwendungen bedeutende Brustschilde-Stempelseltenheit".