For shelf-browsing, the relevant call number ranges in Russian/Soviet history are
DK1 - DK949.5: History of Russia. Soviet Union. Former Soviet Republics
DK33 - DK 35.5 Ethnography
DK36 - DK293 History
DK70 - DK112.42 History: Earliest to 1613
DK70 - DK99.7 Rus'
DK99.8 - DK112.42 Muscovy
DK112.8 - DK264.8 House of Romanov, 1613-1917
DK265 - DK265.95 Revolution, 1917-1921
DK266 - DK292 Soviet Regime, 1918-1991
DK293 1991-
DK500 Regions Not Limited to One Republic, A-Z
DK501 - DK949.5 Local History and Description
DK503 - DK503.95 Estonia
DK504 - DK504.95 Latvia
DK505 - DK505.95 Lithuania
DK507 - DK507.95 Belarus. Byelorussian S.S.R. White Russia
DK508 - DK508.95 Ukraine
DK509 Southern Soviet Union
DK509.1 - DK509.95 Moldova. Moldovan S.S.R. Bessarabia-
DK510 - DK651 Russia (Federation). Russian S.F.S.R.
DK541 - DK579 Saint Petersburg. Leningrad. Petrograd.
DK588 - DK609 Moscow
DK670 - DK679.5 Georgia (Republic)
DK680 - DK689.5 Armenia (Republic)
DK690 - DK699.5 Azerbaijan. Azerbaijan S.S.R.
DK751 - DK781 Siberia
DK845 - DK860 Soviet Central Asia. West Turkestan
DK901 - DK909.5 Kyrgyzstan. Kirghiz S.S.R. Kirghizia
DK921 - DK929.5 Tajikistan. Tajik S.S.R. Tadzhikistan
DK931 - DK939.5 Turkmenistan
DK941 - DK949.5 Uzbekistan