4 Reichmark Polar travel, properly franked single franking on international letter, transported with airship Count Zeppelin, red special confirmation stamp \"airship Count Zeppelin Polar travel 1931\" and special stamp \"ice-breaker Malyguin, the stamp cancelled \"Friedrichshafen (Lake Constance) b 24.7.31\", photo expertize H. D. Schlegel BPP (2022) : \"genuine. Slight traces of use. \"