After one year of preparations involving the production of ten prototypes, the firm was ready to commence the car-manufacturing business within the SKF group. The Volvo Group itself considers it started in 1927, when the first Volvo car rolled off the production line at the factory in Gothenburg.[7] Only 280 cars were built that year.[8] The first truck, the "Series 1", debuted in January 1928, as an immediate success and attracted attention outside the country.[5] In 1930, Volvo sold 639 cars,[8] and the export of trucks to Europe started soon after; the cars did not become well-known outside Sweden until after World War II.[8] AB Volvo was introduced at the Stockholm Stock Exchange in 1935 and SKF then decided to sell its shares in the company. By 1942, Volvo acquired the Swedish precision engineering company Svenska Flygmotor (later renamed as Volvo Aero).[5]