Marconi-Osram Valve Co
- 1919 Marconi-Osram Valve Company formed as company owned jointly by GEC and Marconi's Wireless Telegraph Co; it took over GEC's valve factory.
- 1920 Name of company changed to M-O Valve Co[.
- 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
- Continued to supply valves to Marconi.
- 1956 GEC purchased EMI's share in the M-O Valve company.
- 1969 Formation of GEC Electronic Tubes to bring together M-O Valve and English Electric Valve Co, a company which would have half of UK valve production, the largest specialised valve manufacturer outside USA