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.