Netherlands East Indies. (Ceylon - Postage Dues). 1936. Air Mail envelope addressed to Colombo, Ceylon bearing Netherlands 'Air Mail' Yvert 9, 36c blue and red tied by Leiden date stamp '23rd May' , routed via Karachi with boxed 'Karachi/ Canceled/ 1st May' with Ceylon instructional 'Amount To Be/ Collected...24' on dance and forward to Blora and bearing Netherlands East Indies postage due SG D230, 7 1/2c salmon (pair) tied by Batavia date stamp '17th May' with 'Post, Telegraaf en Telefoondienst' instructional from. Nice combination.