Insured cover used to send 300 roubles to Vindava, franked on reverse 3k, 4k (strip of 3 & single) & 50k Arms issue, cancelled in violet “NO 4 FIELD POST OFFICE / PRIAMUR DISTRICT 18 IX 1905”. Wax seals with same inscription. Blue cachet of 2nd NERCHINSK COSSACK REGIMENT. Blue-lined registration label reads “RESERVE FIELD POST OFFICE No 4” with NINGUTA added by hand. Received VINDAVA, Courland Province (Baltic States) 22 X 1905; opened-out for display. This cover established the location of No4 FPO at Ninguta, Manchuria. Illustrated K.Adler “British Journal of Russian Philately” 16 (1954), page 471. Ex Dr. Casey