1939, SYS 10 C./25 C. and martyr 1 C. (strip-3) tied light blue "Installation of Posts&Telegraphs Dept. 1st anniversary 28.5.19" (May 19, 1939) to reverse of registered cover to Tientsin with next day arrival, commercial usage. Also Mengkiang commemorative postmarks on cto covers (3) or card (1) from Tulun, Kalgan, Datung and Changpe. Total five items. (Image)