Since the Aussig-Teplitz Railway had a network with many gradients, the power of the existing class I 2-4-0 passenger locomotives became insufficient early on. 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 with 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 outside frame. Between 1889 and 1894, 26 more, almost identical locomotives were ordered from the Wiener Neustädter Lokomotivfabrik and designated class IIIb. The biggest difference was that the slightly more powerful boiler was now operated with eleven instead of ten bars.

The locomotives were also used for heavy freight trains, but were mostly found in passenger service. Most survived until the nationalization of the ATE in 1924. They were now put into the CSD classes 322.3 and 322.4. While the older type was completely withdrawn in the 1920s, 13 locomotives of the 322.4 were still available when the Sudetenland was annexed in 1938.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.