The class Z refers to rack locomotives in the Abt system which had three axles and a pure rack drive. They were based on the H 2/3, which the SLM had built for the Monte Generoso railway. Six locomotives were built for the Salzkammergut-Lokalbahn for use on the Schafberg railway, whose bodies were inclined by 17 percent according to the line. The EWA purchased five more for the Schneeberg railway, which were only inclined by twelve percent.

For downhill running they had an additional water tank to cool the cylinders when the Riggenbach counter-pressure brake was used. The Schneeberg railway equipped its locomotives with petroleum firing from 1900 onwards, which was undone during the First World War. In the fifties they received Giesl ejectors. Today all eleven locomotives are still existing, four of them operational.