China. (French Occupation of China). 1889. Envelope addressed to France headed 'Troupes de l' Indo-China' cancelled by 'Hai-Phong/ Tonkin' double ring '13th Jan 89' with bold large circular 'Genie/ Place de Hanoi' on face and reverse, routed via Annam with undated 'CORPS EXPRE/ ANNAM - TONNIN' on face with Nantes arrival '22nd Fevr' on reverse.
See Desrousseaux Type '41a' error 'TONNIN' the Corps Expeditionnaire applied at Caobang.
Desrousseaux notes rarity 'R' few examples known or perhaps unique.