This is third cover sent by Mr. Wolfgang Beyer, Germany, with special postmark obtained at Stade, Germany during the Hansa Day celebration celebrated annually in the month of May at various Hanseatic cities of northern Europe.
The postmark shows Cog (or cog-built vessels) - a type of ship that first appeared in the 10th century, and was widely used from around the 12th century on. Cogs were generally built of oak, which was an abundant timber in the Baltic region of Prussia. This vessel was fitted with a single mast and a square-rigged single sail. These vessels were mostly associated with seagoing trade in medieval Europe, especially the Hanseatic League, particularly in the Baltic Sea region.