Postcard, stationery, Universal Postal Union, retrieved in Wrocław, shipped to Kolding, Denmark, used

In Berne on October 9, 1874, 21 states merged into an international organization under the name "General Postal Union." This regulated, amongst other things, the transportation of postcards for its members.
In 1878 the standardization of the postcard form for use in international postal services was decided upon at the Paris Conference, now called the "Universal Postal Union." A uniform measure (148x105 mm), uniform colors for postage stamps and postage marks, as well as a uniform multilingual text impression for the postcard were determined.