Marconi-Osram Valve
M-OV (Marconi-Osram Valve Company) was a British manufacturer of thermionic valves (vacuum tubes). It was a subsidiary of the (British) General Electric Company Ltd. It was named after the Marconi Company and Osram, which were two major manufacturers of the tube. History 
The company was founded in 1919, when the valve making interests of GEC (Osram) and the Marconi Company were combined. In 1929, Marconi sold its interest in the company to the Gramophone Company, a predecessor of EMI. In 1939, M-OV acquired two disused cotton mills at Shaw, Oldham where it established a shadow factory to produce valves and cathode ray tubes. The two mills named Cape and Duke, were bought from the Lancashire Cotton Corporation for £7,000. Cape mill was used as the main production facility at Shaw, with the adjacent Duke mill remaining mostly unused. Shaw produced a vast array of valves for the war effort, some of which are listed below. VT104 and VT105 for the T1154 transmitter. VR99, VR100, VR101 and VR103 for the R1155 receiver. TT11 for the TR1143 fighter set. VT90 micropup used in airborne radar. EMI sold its share of M-OV to GEC in 1956. The company continued to manufacture valves at the Brook Green Works, Hammersmith, London, until 1988. M-OV branded new old stock valves, continue to be highly prized by enthusiasts of the valve sound. Notable products of the company included cathode ray tubes for television, starting in the 1930s. The company also introduced the KT66 "kinkless tetrode" (beam power tetrode). In 1922 the company brought out valves using thoriated tungsten filaments, which needed less battery power to operate than former types. During World War II the company developed the CV122 valve used in the proximity fuse. As technican in the 1960s I worked in the receiving tube section E4 at the MO valve company that produced low noise triodes, variable mu pentode , corona stablizers and diskseal microwave tubes that operated in the grounded grid configuration inserted into a cathode and plate tuned cavity. Other sections produced CRTs TWTs, klystrons and magnetrons mostly for military applications. With the proximity fuze tubes they were small tubes with flying leads for connection to the electrodes and during testing were fitted into a cylinder and fired at a target with compressed air to test they would withstand the high g force created with the impact with the target. I also believe some of the thyratrons manufactured at the MO valve company  contained tritium a radio active isotope of hydrogen. Bibliography
 Barry Vyse & George Robert Jessop, The Saga of Marconi-Osram Valve: A History of Valve-making at One of the World's Foremost Enterprises, Vyse Ltd, 2000

External links
 http://www.gracesguide.co.uk/Marconi-Osram_Valve_Co

Electronics companies of the United Kingdom
General Electric Company
Electronics industry in London
Defunct technology companies of the United Kingdom
Electronics companies established in 1919
1919 establishments in England