OM Tipo S305 History

The Tipo S305 was Officine Meccaniche's first passenger car, introduced in 1918 when the Milan factory pivoted from railway rolling stock to automobiles. It was derived from the earlier Züst marque — whose assets OM had absorbed — and used a large 4,712 cc inline four-cylinder, side-valve engine, making it a substantial touring car typical of the immediate post-war period.

The S305 was more of a transitional product than a fully original design; its large displacement and conservative engineering reflected the Züst heritage rather than OM's own ambitions (sources vary on how long it stayed in production — some cite an end date around 1919 when the smaller Tipo 465 arrived, others list it continuing to roughly 1923). It set the stage for the lighter, more sporting models that would define the brand through the 1920s.