The archive (excluding Melville Richards's proposed onomasticon) consists of 159 boxes each containing an estimated 2100 slips. The density of material varies from slips with a solitary name to slips with ten or more lines of detail. The slips cover settlements (places) and topographical features (fields, hills, mountains, rivers, streams, bays, promontories etc.).
Most slips will typically have a head-name (usually in standardised spelling), a county, parish or township location, a grid reference (NGR), historical forms (including date and documentary source), and occasionally cross-references to similar names or to relevant secondary sources.
In common with all place-name researchers Melville Richards took his historical evidence from a range of documentary sources: land tax assessments, parish registers, tithe maps and schedules, estate papers, medieval rolls, charters, rentals, terriers and wills, maritime charts, enclosure awards, literary bruts, chronicles, sagas and romances. As far as is currently known, Melville Richards did not keep a formal list of abbreviations of his documentary sources but the vast majority are conventional abbreviations readily recognised by today's scholars. However, there remains a very small number of abbreviations which have defied all attempts at identification.