An early nineteenth century manuscript containing two Unitarian tracts entitled respectively 'Cyfarchiad At Aelodau yr Eglwys Sefydledig ac at Drindodiaid Protestanaidd yn gyffredinol Lle yr annogir ac y cynghorir hwynt I droi oddi wrth Gau-addoliad tri o Bersonau I addoli Yr Unig Wir Dduw' and 'Ail Gyfarchiad At Aelodau yr Eglwys Sefydledig ac at Addolwyr tri Pherson ac un Duw, O Bob Enw'.

The fonds consists of personal papers and correspondence, 1826-1967, of members of the family of Rees Jenkin Jones, namely the Rev. John Jones (1802-1863), Mrs Anne Griffith Jones (1852-1899), Dr Goronwy Jones (1881-1945), the Rev. Simon Jones (1879-1967) and the Rev. Rees Jenkin Jones (1835-1924) himself, together with estate records, 1620-1916, of the Clettwr estate, Cardiganshire, Cilgell Isaf estate, Carmarthenshire, and of premises in Aberdare, Glamorgan. Much of the material relates to the Unitarian cause in Wales.

A collection comprising correspondence, poetry, notes, extracts and miscellanea (mainly relating to religious matters), an account book from Haverfordwest, sermons by several individuals, a journal of Timothy Davies, Caeronnen, and hymns by Reuben Davies ('Prydydd y Coed').