From 1923, the BBÖ had 40 locomotives with a 4-8-0 wheel arrangement and a low axle load built to operate the heavier express trains on the Westbahn. Borrowings were taken from the two prototypes of the class 570, which had been built in 1915 for the Südbahn. Despite the lack of a trailing axle and the maximum speed of only 85 km/h, they had a large grate and a high tractive effort, which allowed them to be used with heavy trains, even in mountainous areas. The Polish PKP had Fablok build 60 very similar locomotives as Os24. The Austrian locomotives came to the Reichsbahn in 1938 as class 331 and later kept the same numbers in the ÖBB. The last disappeared in 1968. Five locomotives had come to Yugoslavia after World War II, where they were designated as class 10. 