Sudan. 1931. Air Mail envelope addressed to Port Sudan bearing SG 47, 5m olive and black (strip of four) tied by Sudan Air Mail/ Malakal date stamp '7th May 31' with 'Air Mail' label, routed via Imperial Airways to Khartoum with 'Sudan Air Mail/ Khartoum' date stamp '7/5' and by train to Port Sudan '10th May' receiver on reverse. Scarce early internal Air Mail.