RAF survey flight 1930, envelope carried on the third stage from Jesselton via Kudat to Sandakan franked at 28 cents with the special framed " AIR MAIL /Aeroplane/ NORTH BORNEO " cachet with despatch datestamp alongside, on reverse the Kudat (2x) and Sandakan cds for 4, 5 and 6 jun resp. Muller 1