The outbreak of WWII reduced dramatically the request for passenger transport during the following years, except for large army convoys which were unsuited to the small Littorine; both Breda and OM converted their production to war effort.
In 1949 the SIF company, manager of the private railway Siena-Buonconvento-Monte Antico, ordered two additional cars to OM; unlike the FS units, which had a 4-number code, these were originally numbered 101 and 102.