Salmson was an engineering company specialising in hydraulic pumps and aircraft engines. Post World War one in 1919, with diminished demand for aero engines, they turned their attention to motorcars, building the V twin GN cyclecar under licence in vast quantities, and the car portion of the company was separated off in 1922. By 1920 they had their own cyclecar type AL with their ingenious valve operating method unique to Salmsons, followed by D Type, VAL3, AL3 Supercharged San Sebastian and long running GS (Grand Sport). Into the 1930's came the S4 series of models starting off at 1500cc, then 1700cc. The 2.3 litre S4E of 1937 reappeared and modernised post war but by 1952 the company was in administration, and the 2300 Sport was still produced in small numbers. Renault bought the factory in 1957, and that was the end of the Salmson name in cars.
Salmson had started a company to manufacture radial aero engines in London, which was bought in 1930 and renamed British Salmson Aero engines Ltd. As engine sales were slow, they got a licence to build Salmson cars in 1934. The 1500cc S4C was as the French chassis but with synchromesh gearbox. For 1937 a new heavier S4D with enlarged 1600cc engine. They built a twin ohc 6 cylinder "S6D" 2.6 litre 20/90 but car production stopped when the war came and afterwards moved location and manufactured other things.