M-O Valve Co
of Brook Green, Hammersmith, London.
1919 Private company.
1920 The name of the Marconi-Osram Valve Co was changed to M-O Valve Co[1].
1920 Jan. Physical and Optical Societies Exhibition. Exhibited wireless telegraphy.
1927 Recorded as being a subsidiary of GEC
1929 Gramophone Co acquired Marconiphone Co as well as Marconi's share in M-O Valve[2].
Continued to supply valves to Marconi.
1956 GEC purchased EMI's share in the M-O Valve company.
1958 Business had been focussed on thermionic devices for telecommunications, radar and military, and cathode ray tubes[3]
1961 Manufacturers of electronic and thermionic valves, cathode ray tubes and devices, magnatrons, hydrogen thyratrons, klystrons, backward wave oscillators, travelling waves tubes, T.R. cells and geiger-muller counters. 1,500 employees.
1969 Formation of GEC Electronic Tubes to bring together M-O Valve Co and English Electric Valve Co, a company which would have half of UK valve production, the largest specialised valve manufacturer outside USA[4].