The contents of the collection include: correspondence, manuscripts, minutes of "Zagranichnai︠a︡ Delegat︠s︡i︠a︡" meetings from the 1920s, and financial records both from the Party organization in Russia (1908-1915) and from its Estonian and Finnish affiliates (1922). The collection's subject files are particularly rich in materials on S.R. groups in foreign countries and on Party infiltrators ("provokatory"), including E.F. Azef. The collection also contains photographs of several prominent S.R.s, including Ekaterina Breshko-Breshkovskai︠a︡; printed materials, including the first five issues of "Sot︠s︡ialist Revoli︠u︡t︠s︡ioner (1927-1932); and seals from the offices of the "Zagranichnai︠a︡ Delegat︠s︡i︠a︡." Correspondents which figure prominently in the collection are: Nikolaĭ D. Avksentév, Viktor M. Chernov, Ili︠́a︡ I. Fondaminskiĭ, Osip S. Minor and Vladimir M. Zenzinov; there is one letter by Azef. Much of the pre-1920 correspondence is addressed to Mark A. Natanson; after 1922 a large number of the letters are addressed to Sergeĭ P. Rostnikov.