on piece 1911 (27 July) "ON POSTAL SERVICE" envelope front registered to Peking bearing 1a. on 4c. with 6a. on 30c. tied by "LHASA.TIBET" c.d.s., India 3a., 1a. and ½z. tied by "YATUNG-TIBET/VIA SILIGURI" c.d.s. and showing both registration marks; most attractive