The published text is a source, includes more detailed information about ambassadorial relations between Russian administration in Siberia and Kuchum Khan’s descendants in the middle of the 17 th century. The document talks about the diplomatic missions of the Tobolsk son of boyar S. Kobylyansky and Cossack head G. Grozin to the Siberian Prince Devlet-Giray in 1645 and 1646. Despite the poor preservation (the document has no beginning and end) «otpiska» is of great interest due to the large number of details and previously unknown details. First, the document contains new information to the biographies of the Siberian Princes Devlet-Giray and Bugay, and Tobolsk service class people S. Kobylyansky and G. Grozin. The last of them was the son of the famous Cossack ataman Ivan Groza. The source also contains new information about the relationship between Kuchum Khan’s descendants and Oyrat-Kalmyk nomads. Siberian princes tried to get support from nomads by the conclusion of dynastic marriages. The document contains many references to such attempts. Also Tobolsk Governors received a lot of valuable information from ambassadorial mission of G. Grozin. According to his information the Central Asian merchants from Buhara brought princes intelligence information on the situation in Siberian towns, and supplied them with weapons and ammunition. Also Grozin found out a lot about the number of people in princes’ «uluses», as well as some peculiarities of their nomadic way of life. Especially important for the Tobolsk Governors was information about the places of summer and winter camps and routes of migrations. This information princes did secret. The document also contains an interesting reference about purposes of predatory raids on the yasak people in Western Siberia. Devlet-Giray usually explained their raids by his need and poverty during the negotiations with Russian authorities. According to other reports, the prisoners were forced to increase the number of their nomadic people. However, Prince Bugay openly called Russian ambassadors and the third reason for the raids. Prisoners could be sold to the Central Asia to receive the big trading profits. At the same time the princes dreamed about the expulsion the Russians from Siberia and the restoration the Siberian Khanate. However, such shortsighted policy was doomed princes to fail. This confirms the futility of their struggle with the Russians in Siberia in the 17 th century.