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 licence 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, Epidiascopes, 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) 
1948 Ross Ltd and Barnet Ensign Ltd were merged to form Barnet Ensign Ross Ltd. Clearly it was hoped that with the addition of Ross's quality lenses to their existing range of cameras, B.E.R. would become a force to be reckoned with.
1954 Renamed Ross-Ensign Ltd; it produced classic 50s roll film cameras, like the Selfix andAutorange, which are still popular today with many collectors.
By 1955 Ross Ensign had moved production from Walthamstow to Ross's Clapham Common factory, where they continued to produce cameras along with lenses and binoculars.
1961 the production of cameras ended but the company continued for some time to sell Ross optical devices such as binoculars or enlarging lenses.
Resources 1922 British Industries Fair p68
1929 British Industries Fair Advert p124; and p145
1937 The Aeroplane Directory of the Aviation and Allied Industries
1947 British Industries Fair p237