Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 146,041 pages of information and 231,556 images on early companies, their products and the people who designed and built them.
of Peel Works, Silk Street, Salford, 3, Lancs. Telephone: Manchester Blackfriars 6688. Cables: "Sparkless, Manchester". (1947)
of Times Mill, Gee Street, Heywood.
1910 Company founded.
1912 Investments in various companies including Salford Electrical Instruments Ltd making measuring instruments; all three companies were directed or controlled by GEC.
1937 Manufacturing electrical engineers. 
1945 Proprietors were GEC
1947 British Industries Fair Advert as Manufacturers of Switchboard, Portable and Substandard Electrical Indicating Instruments; Industrial Electronic Equipment; Magnetic Powders and Cores; Quartz Crystal Units; Radio Cores; Toroidal Cores and Coils; Mercury Switches, Relays, Optical Components and Apparatus; Rectifiers; S. E. I. Exposure Photometers; Photo-cells; Synthetic Sapphires. (Scientific and Optical Section - Olympia, Ground Floor, Stand No. A.1119) 
1958 Maker of components for communications, crystal valves, transistors, electrical instruments and thermostatic devices
1961 Manufacturers of electrical instruments, thermostats, telecommunication components. 1,725 employees. 
1968 The combination of SEI and Chamberlain and Hookham with AEI operations at Motherwell, Harlow and Manchester was expected to make a strong base for competing in meters, instruments and components
1973 SEI was a member of GEC Electrical Components Ltd