Masterpiece from the SLM Winterthur. The cogwheel steamlocomotives of type HG 4/4 were procured in nine copies from 1923 onwards by the French colonial administration for use on the rack railroad from Song Pha to Đà Lạt in French Indochina (today Vietnam). The rack-and-pinion locomotives built by Schweizerische Lokomotiv- und Maschinenfabrik Winterthur (SLM) were taken directly to France and on to Asia, where they remained until the line was abandoned due to the war in the 1970s. Two machines, which were returned to Switzerland in 1990, have been preserved at the Dampfbahn Furka-Bergstrecke (DFB), one of which is still being refurbished. At the time the locomotives were designed, SLM was able to draw on extensive experience in the construction of rack-and-pinion locomotives. The basis for the HG 4/4 was the HG 4/5 rack-and-pinion locomotive with the Winterthur drive system delivered to the Nilgiri Railway in India in six units in 1914 and in another four in 1920. The power output was again significantly increased, and the design without running axles made it possible to use the total mass of the vehicle as a frictional weight. The maximum drivable gradient was 120 ‰, the trailer load on adhesion and cogwheel sections was to be a maximum of 65 tons. SLM had already built the locomotives HG 2/3 and HG 3/4 (Abt system) earlier. Text from Wikipedia, translated. The # 704 is on a warm-up run in the gorge of the Furkareuss near Realp.