Hergé letter from the Belgian Antarctic Expedition

An original letter from Hergé, who was part of the Belgian Antarctic Expedition in 1958. The letter is dated with a stamp from the Antarctic base on 1-1-1958 and arrived in Brussels on 16-3-1958. The letter includes a card from Hergé featuring his famous compass. Name cards are included. The letter has a couple of minor folds, but this is logical, since he actually travelled to Antarctica! An unusual envelope of historical value.