Starting in 1856, Hartmann started to build four 2-4-0T tank locomotives for the Obererzgebirgische Staatsbahn for use in coal traffic. In the years up to 1874, two other companies in the Zwickau coal district followed: the Oberhohndorf-Reinsdorfer Kohleneisenbahn got four and the Bockwaer Eisenbahngesellschaft got two. These locomotives had inside frames, outside cylinders and outside valve gear. While eight had Stephenson valve gear, two had the Allan type.

In 1868, the locomotives of the Obererzgebirgische Staatsbahn came to the Saxon State Railways. There the class designation changed multiple times: from H IV over H IV T, H IVb T and IVb T to IIb T. The “H” originally stood for the manufacturer Hartmann. The “Muldenthal” of the Bockwaer Eisenbahn was the last one that was in line service in 1923. From this year it was used as a works locomotive and was only withdrawn in 1952. Four years later it came into the Dresden Transport Museum and today is the oldest surviving Saxon locomotive.