Hong Kong. (British Post Offices In China). 1917. Registered envelope addressed to Paris bearing British Post Office in China SG 6, 10c blue (pair) tied by Tientsin/Br. P.O. date stamp (Webb Type B) with framed 'R/Tientsin B.P.O.' in red, routed via Shanghai, Vancouver and Montreal with Paris/Chargements arrival on reverse. Very fine.