Stanford Stadium Postcard. 5 1/2 inches by 3 1/3 inches in perfect unused, condition. copyright Stanley A. Piltz. Made of linen. Linen postcards were produced between 1930 and 1945 when a new printing processes allowed printers to produce postcards with high rag content, which gave them a look of being printed on linen, rather than paper. Linen postcards have a beautiful, subtle use of colors.