1830 The Ross firm was founded by Andrew Ross in Wigmore Street, London.
c1840 Ross started making lenses for cameras. The lenses were engraved A. Ross, London. Ross had an early association with Carl Zeiss in Jena; Zeiss licensed some Ross patent designs particularly for EWA lenses and in turn Ross had a license for the British Empire to make some Carl Zeiss lens types.
Zeiss built a factory in London, mainly to produce binoculars; some camera lenses also were produced.
1855 Ross also made some cameras, from about 1855 to the 1910s.
1858 Andrew Ross died, a year before the firm moved premises.
After Andrew died the firm was run by his son T. R. Ross, and the lenses were engraved Ross, London. J. H. Dallmeyer, who had married Ross’s second daughter, Hannah, inherited one third of his employer’s large fortune and the telescope manufacturing portion of the business.
1859 The firm moved to Brook Street with a sales department in New Bond Street.
WWI Ross took over Zeiss’s London factory at Mill Hill.
1921 Charles Parsons acquired a controlling interest in Ross Ltd, of Clapham, where he improved the methods of glass-grinding.
1922 Listed Exhibitor – British Industries Fair. Manufacturers of Cinematograph Projectors, Photographic Lenses, Lenses for Aeronautical Cameras, Photographic Cameras, Prism Field Glasses, Telescopes, Sporting, Military and Naval. (Stand No. G.61d) 
1929 Advert in British Industries Fair Catalogue as an Optical, Scientific and Photographic Exhibit. Manufacturers of Photographic Lenses, Cameras, Prism Binoculars, Field Glasses, Opera Glasses, Telescopes, Terrestrial, Astronomical, Cinematograph Projectors, Search-light Arc Lamps, Equipment, Optical Lanterns, Aeronautical, Astronomical and Nautical Instruments, Lenses, Prisms of all kinds. (Scientific Section – Stand No. O.32) 
1937 Aero lenses, binoculars and telescopes. 
1947 Listed Exhibitor – British Industries Fair. Manufacturers of Cinematograph Projectors, Arc Lamps, Epidiascope, Photographic Lenses, Binoculars, Telescopes, Scientific and Optical Instruments including Autocollimating Goniometer and Optical Benches and Special Optical Systems. (Olympia, Ground Floor, Stand No. D.1692) 
Source London Fine Antiques