Press letter books, 1878-1920, press invoice books, 1878-1919, account books, 1893-1920, and a minute book, 1900-1901.

A copy of 'The Croesor file', comprising Adrian Barrell's and others' research material relating to the Croesor Slate Quarry, Llanfrothen, Merionethshire, from the 1860s onwards (1994 donation). A supplement copy to 'The Croesor file', also including extensive extracts from the Minute Book of the Park & Croesor Slate Co., and a section dealing with the research note books of Moses Kellow, the company's manager and engineer, together with a CD which contains the full autobiography of Moses Kellow (2003 donation).

Papurau llenyddol Bryfdir, 1891-1941, rhai ohonynt wedi eu cyhoeddi, yn cynnwys copïau mewn llawysgrif o farddoniaeth yn y mesurau caeth a rhydd, llawer ohonynt ar gyfer cystadlaethau eisteddfodol,1893-1941; llyfrau nodiadau a chyfrolau eraill yn cynnwys copïau o gerddi a nodiadau ac ychydig o eitemau eraill megis rhyddiaith, torion papur newydd a thystysgrifau, [1891]-[1936] = Literary papers of Bryfdir, 1891-1941, some of which have been published, including manuscripts of poetry in strict and free metre, many of which were written for eisteddfod competitions, 1893-1941; notebooks and other volumes containing copies of poems and notes and a few other items such as prose, newspaper cuttings and certificates, [1891]-[1936].

Papurau Bob Owen yn cynnwys traethodau eisteddfodol, 1910-1941; beirniadaethau ar draethodau eisteddfodol, 1916-1949; crynodebau o bregethau a glywodd, 1895-1927; teipysgrifau rhaglenni radio yr oedd ynghlwm wrthynt, 1936-1957; gohebiaeth, 1908-1961, yn cynnwys llythyrau Dr Thomas Richards, 1923-1960; dyddiaduron, 1905-1961; papurau personol, 1898-1961; papurau teuluol, 1900-1923; copïau a drafftiau o ddarlithoedd, erthyglau a thraethodau, 1906-1950; nodiadau ac adysgrifau helaeth ganddo o farddoniaeth Gymraeg, ewyllysiau a mynegeion ewyllysiau, cartiau achau ac achresi, cofrestri plwyf ac adysgrifau'r esgob, dyddiaduron, llythyrau, almanaciau, cofnodion llys, yn ymwneud yn bennaf â siroedd Caernarfon a Meirionnydd, a chofiannau, [20 gan., ½ cyntaf]; nodiadau ar anghydffurfiaeth yng Ngogledd Cymru, plwyfi siroedd Meirionnydd a Chaernarfon, llongau a morwyr o Gymru a Chymry Llundain, [20 gan., ½ cyntaf]; nodiadau pwysig ar ymfudo o Gymru, yn enwedig i'r Unol Daleithiau, [20 gan., ½ cyntaf]; copïau teipysgrif o gofnodion corfforaethau yn cynnwys Parc Cenedlaethol Eryri a Chyngor Sir Feirionnydd, 1922-1962; cofnodion gwreiddiol a ddaeth i feddiant Bob Owen, yn bennaf cofnodion Chwarel Parc a Chroesor, sir Feirionnydd, yn cynnwys cyfrifon a chofnodion, 1891-1941, a chofnodion ysgolion ac ysgolion Sul, 1861-1957; a thorion ac adysgrifau o amrywiol gyfnodolion Cymreig, 1816-1965. = Papers of Bob Owen including eisteddfod essays, 1910-1941; adjudications of eisteddfod essays, 1916-1949; summaries of sermons heard by him, 1895-1927; typescripts of radio programmes involving him, 1936-1957; correspondence, 1908-1961, including letters from Dr Thomas Richards, 1923-1960; diaries, 1905-1961; personal papers, 1898-1961; family papers, 1900-1923; copies and drafts of lectures, articles and monographs, 1906-1950; extensive notes and transcripts by Bob Owen of Welsh poetry, wills and indexes of wills, pedigrees and genealogies, parish registers and bishops' transcripts, diaries, letters, almanacs, court records, mainly relating to Caernarfonshire and Merionethshire, and biographies, [20 cent, first ½]; notes on nonconformists in North Wales, Merionethshire and Caernarvonshire parishes, Welsh ships and sailors and the London Welsh, [20 cent, first ½]; important notes on emigration from Wales, especially to the United States, [20 cent, first ½]; typescript records of bodies including Snowdonia National Park and Merioneth County Council, 1922-1962; original records acquired by Bob Owen, mainly records of Parc and Croesor Quarry, Merionethshire, including accounts and minutes, 1891-1941, and school and Sunday School records, 1861-1957; and cuttings and transcripts from various Welsh periodicals, 1816-1965.