Since the No. 2501 to 2540 ten-wheelers had drivers too small for express service, the French Ouest took these as basis for a new type of express locomotives built from 1901. They got larger drivers with a diameter of 1.910 instead of 1.750 mm and were otherwise very similar. Like their basis, they were four-cylinder de Glehn compounds. Of the first 20 locomotives, the first ten were right hand drive and the rest left hand drive.

The next 50 locomotives still had a boiler with a Belpaire firebox and serve tubes, but now had piston instead of slide valves. The last 50 were only built by the German companies Borsig and Henschel and had a superheater. The SNCF designated them 230 C. After the Ouest was taken over by the État, they ordered 85 identical locomotives in 1912 and numbered them 621 to 705.