After the first order for four of these units built by Ateliers Saint Léonard (Belgium) and numbered from 401 to 404, another 5 were commissioned from Ateliers de la Meuse (Belgium) and numbered from 405 to 409. The first batch was characterized by robust superheated steam locomotives powered by 2 twin cylinders. The main difference with respect to the first batch was the position of the dome that was moved forward and further away from the steam furnace. In addition, the boiler was fed through a Friedman injector and not through a donkey pump used in the previous cars. The addition of these two units was designed to meet the increasing demand for passenger and freight train configurations and the weight required to support them.
Later, a new batch was ordered numbered from 406 to 411. Only cars from 405 to 411 changed their name after 1942. The first 4 locomotives were sold between 1937 and 1940. In 1953, the locomotive 405, later called 240-05 was sold to the Company Emilio Astengo of Savona for port shunting work. In 1976, when the boiler life cycle ended, it was set aside and bought again in 1981 by Ferrovie Nord Milano. In 1997, it was restored back to its original look and was included among the historical locomotives owned by LeNORD.