Zeppelins - Germany / USA. 1928 Cover from New York to Switzerland franked $1.05 in air stamps, carried by Graf Zeppelin to Friedrichshafen with arrival backstamp and flight cachet; and 1936 Hindenburg flight covers comprising March 23rd trial flight with Hindenburg air stamps cancelled "LUFTSCHIFF / LZ 129" c.d.s, May 4th registered cover carried on the first flight to USA, and May 11th cover from New York to England franked 40c carried on the return flight to Frankfurt. (4).