Paris-Orléans No. 6001 to 6070

Beginning in 1909, the Paris-Orléans procured a series of 2-10-0 freight locomotives which had been developed from the Pacific express locomotives of the series 4501 to 4600. The four-cylinder compound engine was also adopted from these, which ensured exceptional performance when used in a heavy freight locomotive. The boiler could not be taken over unchanged because the firebox would not have fitted completely between the coupling wheels. However, the slightly shorter boiler also has a trapezoidal firebox, which in this case starts above the fifth coupled axle and then tapers to fit with the lower front end between the wheels of the fourth coupled axle. 

They were stationed around the Massif Central and hauled freight trains of up to 1,200 tonnes. The performance profile still permitted around 750 tonnes at 20 km/h on a gradient of one percent. Although they were not actually designed for this role, they even pulled express trains on the demanding mountain routes. A total of 70 examples were built in three batches by different manufacturers until 1913. Initially, small two-axle models were used as tenders, which offered space for just twelve cubic meters of water and weighed less than 30 tonnes when loaded. Apparently, this had been considered sufficient, since there was no need to run long distances non-stop. In the second and third series, three-axle tenders with a water capacity of 20 cubic meters were used.

The first production locomoties were not without problems, but with the exception of the occasional overheated axle bearing, all problems could be eliminated. They were later modernized, starting with cloverleaf-shaped blast pipes in the 1920s. From 1929, eleven engines were fitted with even more efficient Kylchap induced draft systems, which reduced consumption, and from 1930 a total of 30 units were fitted with different superheaters. André Chapelon used one locomotive as the basis for his six-cylinder locomotive 160 A 1. When the SNCF was founded, the remaining engines were redesignated as the 4-150 A 1 to 70. As early as 1940, the electrification of some routes in the Massif Central meant that these steam locomotives were no longer needed there and were relocated. After the Second World War, despite their age, the locomotives continued to be an important item on the non-electrified routes due to the lack of alternatives. The last example was finally retired in 1955 after the engines had been replaced by diesel locomotives.