The X c was a series of 0-6-0 passenger locomotives for hilly lines. They had inside frames, inside Stephenson valve gear and outside cylinders. On inclines of 1.25 percent, 170 tonnes could be hauled at 22 km/h. A driver diameter of 1,524 mm or five feet was adequate for passenger trains on the level.

From 1868, their designation changed to “VI old”. In the same year, production switched to an updated variant. This had a larger grate, more tubes, a higher boiler pressure and a full cab with side windows.

In 1882, a train with 28 passenger cars led by the locomotive “Kniebis” derailed on a downhill section at Hugstetten, killing 69 and injuring more than 200. Although this accident could be attributed to the brakemen in the train, the speed of this class of locomotives was afterwards limited to 50 km/h.

After that, these locomotives were removed from passenger service and used for freight and switching service. Almost all were withdrawn between 1894 and 1907. The last ones were gone by 1918.