1909 (26 Sept) Rare red band cover from Urga to Kalgan bearing on the reverse 1899 issue 7k overprinted 'KITAI' for the Russian PO in China, cancelled with the Urga Type 6 datestamp which is very rare on 'KITAI' stamps. Incorrect date on Kalgan datestamp

"1909 (26 Sept) Scarce red band cover from Urga to Kalgan bearing on the reverse 1899 issue 7k overprinted 'KITAI' for the Russian PO in China, cancelled with the Urga Type 6 datestamp which is very rare on 'KITAI' stamps. On the reverse: delivery datestamp of the Russian P.O. of Kalgan (Type 3), erroneously dated 2 August (instead of 2 October). the clerk must have turned the month-reel backward instead of forward. The Chinese manuscript delivery records confirm that the letter was received in Kalgan in October. The Type 6 datestamp is inscribed ""Urga v Mongolii Zagr P.K."" (Urga in Mongolia, Post Office Abroad). It shows the serial letter ""a."" This postal marking on 'KITAI' overprinted stamps is very rare and not described in Tchilingirian catalog."