Sections A-C contain many thousands of invoices, receipts, cash books, quotations and estimates, contracts, journals, wages records, production records and order books, and any other type of record relating to the daily administration of the business (1843- 1994).
Section D is comprised of thousands of incoming letters and a much lesser volume of copy outgoing letters, arranged in sub-series exactly as created: in bundles of alphabetically filed letters, bundles of letters filed by month and year, letterbooks of copy outgoing letters, correspondence arranged by owner, legal correspondence and some smaller files or correspondence with government departments and millers’ associations (1873-1964).
Section E is an artifically created series containing correspondence, statements of account and advice notes relating to the distribution of grain into and out of Belmont Mills (1874-1947).
Section F is an artificially created series of correspondence, receipts, policies and schedules relating to the extensive insurances taken out on the mills and on the lives of the owners (1874-1936).
Section G is an artificially created series containing investment policies, banking receipts and debtors’ bankruptcy papers (1873-1954).
Section H contains posters, labels, signs, and packaging relating to the marketing of Belmont Mills products (c.1900-1950).
Section J contains income tax receipts, personal correspondence, and account books relating to the Church of Ireland, personal household expenses, and Lisderg Farm (1858-1975).

Legal agreements in the form of deeds and indentures relating to the Derenzy family’s title and interest in lands in the vicinity of Tinnycross, County Offaly. The earliest deed dating from 1630, records Sir Mathew de Renzi purchasing the townlands of Ballynashragh, Ballycosny, Tyrenehinan, Kilmore and Derry, all in the barony of Ballycowen, on behalf of his son Mathew DeRenzy, then at the bar in London. The vendor was Robert Branthwaite of London, who had been granted the land by letters patent of King James I. Further adjoining townlands of Rossnagouloge or Cappanure were purchased by Sir Mathew from Allen Jones in 1630, and the following year the adjacent townlands of Derrykilliagh and Kilbeg were purchased from Art McOwen O’Molloy. All were settled on his son, Mathew DeRenzy.
The bulk of the collection consists of numerous leases and mortgages raised against the land by Mathew DeRenzy between 1699 and 1703, while he lived at Cloghbemon in County Wexford. Later items in the collection relate to the sale of the lands to Reverend James Cox, Archdeacon of Ferns.

National school records from various primary schools in Offaly and bordering townlands. Mainly contain registers and roll books concerning, respectively, the registration and the daily attendance of pupils; and also smaller amounts of other records such as daily attendance statistical report books and inspectors books.
The registers record a pupil's name, age, and date of birth, and the address and occupation of parents.