China. (Manchuria - Japanese Occupation of Korea). 1915. Registered Official Mail envelope headed 'On His Britannic Majesty's Service' addressed to 'The Secretary, Serbian Relief Fund, Oxford Street, London' bearing Japan SG 164, 20s claret tied by Keijo (Seoul)/ Chosen' date stamp in violet '1st Sept 15' with hand-struck 'Registered' , boxed vernacular instructional 'via Siberia' and vernacular hand-stamp on left, routed via Manchurian railway with oval 'I.J.P.O. Mukden - Changchun/ South Manchuria' in violet dated '2.9.15' and Provisional registration label 'I.J.P.O. No 1/ Mukden - Changchun' with London receiver applied on reverse '20th September 15.'
Registered mail via the Manchurian railway is extremely scarce, this is only the second example of the registered label I have seen, (The other on a registered FRONT to France).