After the KCS had been a friend of Mallets for a long time, they procured a total of ten locomotives with the wheel arrangement 2-10-4 in 1937. Five each were coal and oil fired. This was the first time a boiler of this size has been used with a boiler pressure of 310 psi or 21.4 bars. They achieved an indicated power of 4,825 hp and minus the mass of the locomotive and tender there was still 4,475 hp left at the draw bar. During the Second World War, they were also used to transport troops, and with their 70-inch driving wheels they were able to keep to the timetables of passenger trains. They were replaced by diesel locomotives in 1952 and 1953 and scrapped in 1954.