1936 (15.9.) A. de Bruijn - Netherlands: Cover flown by rocket "RBO" from IJsselmonde to Bolnes, bearing the blue vignette and three Dutch adhesives all tied by hexagonal datestamp. Cover with minor imperfections, but a scarce item. (Old catalogues noted that only 12 covers were flown, but meanwhile some more were discovered, according to Hopferwieser.) (Image)