The content consists of Cubbon's (personal and business) correspondence relating to subjects such as, his MA from Liverpool, his Norwegian knighthood, the Manx language society and the North American Manx Society. Notebooks, a sketchbook, scrapbook, ledger and bills and invoices belonging to Cubbon are included. Account books belonging to Cubbon's father are also present.
Other content relates to Cubbon's work (and interest) in archaeological matters, such as the Manx archaeological sites of Billown Stone Circle, Knocksharry, Cashtal yn Ard, Cronk yn Howe and Treens (general). Items include a large scrapbook containing notes, original plans, prints, draft reports and published reports of archaeological sites. Other notes, plans, reports, discuss subjects such as Manx Crosses, Norse Heritage, the Hebrides, lectures given by Cubbon, a Cumbrian archaeological visit, the Manx Antiquarian Society and the Celtic Society. Further archaeological items include maps of prehistoric sites on the Island, notes on the Manx Museum archaeology collections and an index of the Museum prints and photographs.
Papers on Manx history, the Manx Church (and architecture), Manx place names, Manx parishes, the Manx language and Manx legislature (Tynwald) are enclosed within the deposit. A collection of notes, press cuttings, and correspondence regarding the Celtic Congress are present. Other items within the deposit include genealogical research notes on names for example, Brown, Corlett, Cosnahan, Cubbon, Daugherty , Kermode, Quinney and Stowell.
Material relating specifically to the Manx Museum includes correspondence, notes, lists, old library accession cards, and index of portraits, poems, prose and articles on the Museum and Manx topics are present. Various archival transcriptions of 16th-19th century manuscripts conducted by Cubbon (and others) are included, for example, Libri Assedationis (Lib Assed), Libri Vastarum (Lib Vast), 'The Saga of Sigurd the Volsung', Kirk Malew Abbey Demesnes, a book of wills from the Manx registry office and the Manx Manorial Roll.
Examples of printed material within the deposit includes a copy of Sea Breezes (1936), Betsy Lee , a copy of the Jubilee of the Isle of Man Times (1911), two tourist board maps of the Isle of Man, a copy of Antiquaries Journal (1935), Heraclitus Ridens , and The Annuals of Kirk Christ Lezayre . Miscellaneous items include an envelope containing 'Musical Herald' competition essays, a notebook recording the amount of paper used in the printing of the Peel Chronicle and the Ramsey Chronicle and a programme for the 100th anniversary of the Mona's Relief Society.