Liechtenstein. November 2, 1929, Zürich-Dübendorf Flight mixed franking cover to Basel, franked by 10rp yellow green in block of four and Prince Johann 35rp brown and black, uprated by three Swiss air post adhesives, Friedrichshafen ''2.Nov.29'' connection and Zurich the same day drop ds, VF and scarce cover, Est. $350-$400 (Image)

Liechtenstein. May 12-14, 1931, Baltic Sea Flight postcard, franked by three air post values, tied by Triesenberg ''4.V.31'' ds, Friedrichshafen ''12.5.31'' connection, violet confirmation marking and Copenhagen ''14.5.31'' dropped ds, fresh and VF, Sieger #108, Est. $150-$200 (Image)

Liechtenstein. June 10, 1931, Vaduz and Lausanne Flight postcard and cover, franked by Zeppelin stamps of 1fr and 2fr respectively, red confirmation cachet and all appropriate markings, VF, Sieger #110A, B, Est. $300-$400 (Image)

Liechtenstein. July 24-27, 1931, North Pole Zeppelin Flight postcard from Triesenberg, franked by three stamps, including the high value of 1930 definitive set, Friedrichshafen ''24.7.31'' connection, ice-breaker ''Malygin'' ''27.VII.31'' special drop ds, slight top right corner fold, still VF, Sieger #119, Est. $200- $250 (Image)

Liechtenstein. June 28, 1932, Switzerland Flight (250th Flight of Zeppelin) postcard, franked by three air post values, tied by special blue marking, Vaduz and Friedrichshafen ''28.6.32'' date stamps are alongside, VF, Sieger #167, Est. $120-$150 (Image)

Liechtenstein. July 30-31, 1932, Luposta - Danzig Flight cover, franked by seven air post stamps, including a complete set, tied by Vaduz ''27.VII.32'' ds, Zurich ''28.VII.32'' transit, green Danzig confirmation cachet and Rönne dropped ds, mostly VF, Sieger #170, Est. $200-$250 (Image)