SNCF 232-S streamlined steam locomotive, late 1950s

This was a group of four streamlined 4-6-4 "Hudson" (or Baltic) type express passenger steam locomotives designed by Marc de Caso. They were ordered by the Chemin de Fer du Nord but delivered directly to the newly formed SNCF in 1941. 
They were built alongside the mechanically simpler, 3-cylinder 232-R class to directly test the efficiency of 4-cylinder compound expansion against simple expansion at high speeds. 

They were originally planned in the 1930s  to haul heavy, high-speed express trains. Their service life ended in 1961.

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