To open the new line from Filisur to Davos, the RhB needed new locomotives that had to have sufficient tractive effort on the line, which had a gradient of up to 3.5 percent. Above all, it should not only be possible to transport passenger trains, but also the mixed trains that were common on the RhB. As with the G 2/2+2/3, a Mallet was procured with four coupled axles, but the carrying axle was now at the front. A total of eight locomotives were built in 1902 and 1903 at a price of 76,800 Swiss francs each.

Like its predecessor, the G 2/3+2/2 had an outer frame. This ended at the front at the pivot point of the bogie, so that the boiler overhanged the front without a frame. The starting valve of the four-cylinder compound engine was activated automatically when the reverser was put to the extreme ends. Thus, live steam with reduced pressure was then admitted into the high-pressure cylinders in order to obtain a higher tractive force for starting. The locomotives could transport 300 tonnes at 38 km/h on the level or 90 tonnes on the 3.5 percent of the new line at 20 km/h. However, there was a limit of 18 km/h on the line.

Since the entire RhB network had been electrified by 1920, the locomotives became superfluous. Three units were sold to the Chemin de fer Yverdon-Ste-Croix (YStC) and had just been fitted with a superheater in the RhB workshops. They were used there until 1946, when this railway also electrified its network. This meant that two of these locos were sold to Spain and after several changes of operator were scrapped in 1961 and 1969. The other five were sold to Madagascar and converted to 950 mm gauge. One of them was scrapped in 1930, but the others only in 1958.

At the beginning of the century, the Brünig line, the only narrow gauge line of the Swiss Federal Railways, needed new, more powerful locomotives for the adhesion section in the lower sections. While the previous locomotives only had three coupled axles, the new G 3/4 got an additional leading axle. Only numbers 201 and 202 were built in 1905. Six followed in 1912 and 1913, of which only the last one, No. 208, had a superheater from the start.

In the middle of the twenties, all others were superheated, too. After the top speed had been 45 km/h from the beginning, they were approved for 55 km/h in 1930 and for 60 km/h in 1936. After the Brünig line had been electrified in 1941 and 1942, they came to the Réduit, what was the Swiss system of fortifications and hidden gun positions.

After the war, three locomotives could be sold to the Thessalian railways in Greece. Two were scrapped already in 1947 and the rest got other tasks in Switzerland. 207 and 208 were the last ones to be retired in 1965. 208 was preserved as one of two SBB narrow gauge steam locomotives and was operational until it got damaged by a fire in 2013. In 2016 it came to the RhB shop at Landquart to be restored again.

When it opened in 1884, the meter-gauge Tramelan-Tavannes Railway procured two small tank locomotives from the SLM, which were intended to be able to cope with the line, which was then up to four percent steep. They had a 0-4-0WT wheel arrangement and used their frames as a water tank. For safety reasons, the chassis was protected on all sides with a wooden plank.

Schematic drawing with dimensions

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In 1891 a third, almost identical locomotive was purchased. These locomotives were actually a bit too small for the line, but they remained in use until electrification in 1913. Since other meter-gauge lines in Switzerland were subsequently electrified, the locomotives were rented out for the construction work. After some time in reserve they were scrapped in 1940 and 1943.