On its 40 km line from the port near Rio de Janeiro to Teresópolis, the Estrada de Ferro de Teresópolis had a 10 km section with the Riggenbach rack system and a gradient of up to 15 percent. For this section, the Swiss SLM built a rack locomotive in 1923 that got the running number 21.
It had two carrying axles in the frame with the rack drive between them. The two rack wheels were connected to the cylinders with a gear ratio of 1 to 2.21. At the rear end there was an additional Bissel axle. The boiler was inclined to match the average gradient of the track and to ensure an even water level. 