The majority of this archive consists of letters by Duff to members of his family, viz.: (A): to his wife Laura, 45 letters, 1897-1909; (B): to his son Alan, 356 letters, 1909-1933; (C): to his son Patrick, 96 letters, 1909-1934; (D): to his son James, 4 letters, 1909-1916; (E): to his daughter Hester, 8 letters, 1933-1934; (F): to his daughter Mary, 1 letter, 1911.
There are also 68 letters (G) from Laura Duff to her son Alan, 1915-1940, and three (H) to her husband J.D. Duff, relating to their son James's entrance examinations for Wellington College in 1910. J, K and L are letters written by their sons: 3 letters and a postcard from Alan Duff to his mother, 1909-1920 (J), a letter from James Duff to Alan Duff, 1911 (K), and a letter from Patrick Duff to J. F. Duff, relating to J. F. Duff winning a scholarship to Trinity in 1916 (L).
The final group of letters (M) are by various authors: one from J. D. Duff to Diana Frances Crawley, future wife of his son Alan, on the death of her father, 1933; letters to A. C. Duff from W. G. Collett (1911) and R. Moore (1913) at Wellington College; letter to J. D. Duff from G. M. Trevelyan, 1934 about Edward Fitzgerald's letters; letter to Laura Duff from the Postmaster at Cambridge, 1923, relating to a telegram from Cairo.
Miscellaneous material (N) comprises: copy of the marriage certificate of James Duff Duff and Laura Lenox-Coningham, 1895; page torn from a notebook with short phrase in Ancient Greek; memoir, "Lemnos" of an army camp, probably by A. C. Duff, with envelope addressed to J. D. Duff.
Finally there are twenty eight of J. D. Duff's pocket diaries (usually by Lett's) dating from 1888-1912, 1915-1918, 1922-1926, and 1931-1934; the earliest are kept as appointment books, with brief notes of college and social occasions, but Duff's entries later expand to be fuller records of his days, typically recording weather, reading material, pastimes and family news. A notebook with A. C. Duff's name and address at the front contains 'Extracts from F[ather's] Diary'.