After the Brienz Rothorn Railway (BRB) had lost passengers after they had replaced steam by diesel locomotives, they had the idea to get more popular again among tourists by ordering new steam locomotives. They got support from the Chemin de fer Montreux–Territet–Glion–Rochers-de-Naye (MTGN) and the Schafberg Railway in Austria that was operated by the ÖBB, since these two had the same idea. So SLM was ordered to build modern rack locomotives which could be operated by a single person to reduce operating costs.

The locomotives have a rack-only drive mounted between two non-powered axles, and a trailing axle. They are being fired by light oil and don't need to be lubricated while in service. The water in the boiler can be pre-heated electrically. The boiler and cab are inclined by twelve degrees. In 1992 and 1996, the BRB got three, the MTGN one and the ÖBB four. In 2005, the locomotive of the MTGN was sold to the BRB. The locomotives of the ÖBB now belong to the Salzkammergut-Lokalbahn, the new operator of the Schafberg Railway since 2006.