New CWIL sleeping car Ub 3951, ep.III The sleeping car Ub 3951 is one of the first units to be converted with a single vestibule as early as December 1965; it is a unit of the 3933 – 3962 series built in 1950 by the Compagnie des Entreprises Industrielles Charentaises, easily recognizable by the lower edge of the body covering the frame. This car first served in the French fleet, then in Austria and finally in Germany, almost always operating on international trains.