“SERGIEVSKI POLIGON 11. 8. 11” SERGIEVSKI ARTILLERY POLIGON cds., super as receiving mark on postcard with travelling post office “RIGA 39 TAPS 10. 8. 11” addressed to the Artillery School, very fine and very scarce, this artillery facility in the St Petersburg province had a civilian temporary post office opened from 1st May to 15 September
