b'52128128C 31 May 1928 (AAMC.122a) USA - Australia cover addressed to Lieut CTP Ulm flown by Charles Kingsford Smith, Charles Ulm, J Warner & H Lyon on the first crossing of the Pacific by air endorsed Honolulu to Australia per the Southern Cross/This Envelope was carried across the Pacific Ocean from Hawaii to Australia signed Jas W Warner, Radio Opr and also signed C Kingsford Smith and Lieut Comdr Harry W Lyon, Navigator alongside on face, franked with KGV 1d black-brown tied Sydney 15JE28 datestamp on arrival, very fine condition, only 6 flown, Cat. $12500. Philatelic Foundation Certificate (1973). Ex Frommer, sold for $9000 in the September 2016 sale of his Grand Prix Pioneer AustralianAir Mails Collection. $8,00010,000'