Air Mail cover 1927 (28 June) Dutch trial flight from Amsterdam to Batavia carried on the Bangkok to Batavia leg, a bluish green envelope bearing 1925 Air 2s., 3s. and 10s. cancelled by Don Muang c.d.s. and showing "BY DUTCH PASSENGER SERVICE/OF THE ROYAL DUTCH AERIAL NAVIGATION COMPANY". Fine and scarce. Muller 19