China. (French China). 1906. Envelope made from 'Balsa wood' addressed to France bearing French China SG 38, 10c carmine tied by Chefou-Chine Poste Francaise double ring '16th June 06' with French Post Office Shanghai transit '19th July' on reverse and Loire arrival '25th Aout'. Superb.
Not many Balsa Paper envelopes from Hong Kong or China have survived due to the delicate nature of the paper.