1930 (May 6) legal size envelope for G.M.Hart, U.S. Geological Survey, Washington, D.C. franked with $1.30 and $2.60 Zeppelin adhesives, with Europe-Pan-America Round Trip flight cachet and "This Article Made the Complete Round Trip Via Graf Zeppelin", Friedrichshafen and New York pmks on back, v.f. (Cat No. C14,15) (Image)

Est.$300

1937 Round the world "Airplane plus Zeppelin" cover endorsed "By Trans-Pacific Route to Hong Kong, thence by fastest route to Frankfurt, thence by Zeppelin to the United States". Actually the cover "almost made it" to be flown on the ill-fated Hindenburg 1st flight (in Frankfurt on April 29), but got delayed in processing, and thus avoided destruction, eventually arriving in the United States in June 1937, attractive United States, Hong Kong (Jubilee set) and German franking and appropriate cancels (Image)

Est.$250