Los-Nr. 200

1919, Field post letter insured for 400 rubles with field post cancel "FRONTOWA POCZTA POLOWA No.37 a 13.XII.19” and red sender cachet to the General staff in Warsaw with violet arrival mark “GLOWNA POCZTA POLOWA/w WARSZAWIE a 16.12.”, reverse with five wax seals, cover opened out for display and with tiny spots