Since the Aussig-Teplitz Railway had a network with many gradients, the power of the existing class I 2-4-0 passenger locomotives was no longer sufficient at a relatively early time. For this reason, starting in 1869, a total of nine class IIIa six-coupled tender locomotives were ordered from Hartmann, which were primarily intended for use in front of passenger trains. Compared to class IIa and class IIb freight locomotives, they had larger wheels with a diameter of 1,370 mm, which allowed higher track speeds. Like the freight locomotives, they had a large Kobel chimney and internal valve gear, but unlike these no external frame. Between 1889 and 1894, 26 more, almost identical locomotives were ordered from the Wiener Neustädter Lokomotivfabrik and designated as class IIIb. The biggest difference was that the slightly more powerful boiler was now operated with eleven instead of ten bars.

IIIb No. 14 “Rauschengrund”

The locomotives were also used in front of heavy freight trains, but were mostly found in front of passenger trains. Most engines survived until the nationalization of the ATE in 1924. They were now classified in the CSD classes 322.3 and 322.4. While the older type was completely phased out in the 1920s, 13 examples of the 322.4 were still available when the Sudetenland was annexed in 1938. The Reichsbahn gave them the numbers 53 7401 to 53 7413. Since they remained in their area of operation during the war, they returned to the CSD in 1945 and were singled out shortly thereafter.