In 1932–1934 the two first numbers in the first model names, for example S-321 and S-342, included the year of introduction. The last number indicated the wheelbase. Between 1934 and 1942 the model name included one or two letter after the "S" showing the engine type and a number indicating the wheelbase: SH-1 was with Hercules engine and short wheelbase. The engine manufacturer code was dropped off in 1943 when SAT started its own engine production, and the number in model meant the sequence of the model series, S-21 as an example; the model series numbering was in use until 1983. The engine code made a return for period of 1946–1948 and now the first letter indicated if the model was bus chassis or a lorry: LG-51 meant bus (""linja-auto"") and G stood for Sisu AMG engine.