Aden. (Kathiri State of Seiyun). 1957. Registered Air Mail envelope addressed to Switzerland bearing 'Kathiri State of Seiyun' SG 29, 5c sepia, SG 30, 10c blue, SG 31, 15c green and SG 35, 1s orange tied by Seiyun/ Reg large double ring '6th Aug' with Seiyun/ 0582' registration label, routed via Mukalla and Aden/ GPO Reg on reverse '16/8' and Zurich arrival '27th Sept' on reverse.