1923-06-26, Peking - Tientsin, 5 picture cards showing airplanes, all franked with a different airmail stamp from the set, flown Tientsin - Peking on 06-26 with boxed airmail postmark "Tientsin to Peking" on the backside; a magnificent grouping in excellent condition
6; Flugpost; FLUGPOST INTERNATIONAL; China