FIRST DAY LETTER 1.4.1851 - Royal Service Military letter inside dated 30 March 1851 sent from Flensborg to Viborg stamped “FLENSBURG 1.4.1851” Antiqua IIa, which are the first date when stamps were introduced in Denmark, in Schleswig from 1 May 1851. The letter is sent from “Fra det 5te Dragon Regiments 3. Squadron” -