Archival material relating to the firm of H.N. Irving & Son, instrument makers. Includes: catalogues; photographs of telescopes; order books c. 1950 – 2005; blueprints for telescope designs, including for the restoration of Brayebrook Observatory; material relating to manufacture and international distribution of hypsometer “test baths” for National Physical Laboratory; planetary drawings by Patrick Moore; Certificate presented to Bert Irving by de Havilland Corporation including illustrations of aircraft and a photograph showing members of the Irving family; Company correspondence and records.