Postcard Envelope with Image of Castle, by Curt Teich & Co, 1936, Smithsonian Archives - History Div, Color envelope for postcards, with an image of the Smithsonian Institution Building, or Castle, on the left side. The envelope is numbered "D-4716," which indicates that its initial printing was in 1936. The envelope currently contains a set of 10 unused postcards for the United States National Museum, which was the administrative name for the Smithsonian's museums. Today these collections can be found across the Institution's buildings and museums..