RAF coral survey flight 1931, envelope carried on the first phase of the air survey flight by flying-boat S.1162 (pilot : squadron leader Livock) from Brunei to Singapore (addressed to Livock himself), franked with 30 cents Brunei river, cancelled by Brunei cds 6 april with framed AIRMAIL/BRUNEI chop alongside and showing on reverse, arrival datestamp of 9 April. A very rare cover as only ten items of mail were carried. Muller 3