1931 DORNIER DO-X / airmail letter sent to Curacao by flight of waterplane Dornier Do-X, i.a. franked with stamp 20C with red additional-printing, Mi.161, black round special postmark flight EXTRA LUCHTPOST VERZENDING UIT SURINAME PER To X 18.8.31 and violet flight cachet, on reverse arrival postmark CURACAO 25.8.31