1929 (4 June) flown cover from Ulan Bator to Harbin, franked with 10m, 20m and 25m, tied by cds, with Air Post in Cyrillic (Vozdushnaya Pochta) handstamps applied twice, Chinese Postage Dues 5x4c dark blue added on arrival in Harbin (16.6.29), some toning, otherwise fine (Image)