China. (France - Yunnan Province). 1906. Envelope (with letter) addressed to 'Monsieur Georges Sergent, Ingenieur aux Chemins de Fer du Yunnan (Chine), Mengtze, par Haiphong' bearing France "Sower" 15c green tied by Paris date stamp '10th Feb 06' with Hanoi transit '21st Mars' and Lao-Kay '23/3' with Mong-Tseu-Chine' arrival '4th Avril' on reverse.
Mail into Yunnan Province is very scarce. See Desrousseaux.