The G 4/5 was created in 1904 after a saturated two-cylinder compound 2-8-0 built by SLM for the Ethiopian CFE in 1902 had been tested on the RhB network. The RhB received the first four, numbered 101 to 104, in 1904 which were largely identical to the Ethiopian locomotives. The second and fourth driving axles had lateral play of 40 mm. Although top speed was only 45 km/h, they had to haul both freight and passenger trains on the steep passes. Initially the requirements included that the G 4/5 had to haul a train of 90 tonnes up an incline of 3.5 percent with 18 km/h, but in the result they accomplished this with 22 km/h.
From the next order of four that was built in 1906, only the first two were built as saturated two-cylinder compounds. The other two, numbers 107 and 108, were built as superheated simples. All these four had tenders with 9,800 litres of water and 2.5 tonnes of coal, since the original two-axle tenders with 5,000 litres and 2 tonnes were too small. Production was completed in 1915 when a total of 29 had made them the largest class of locomotives on the RhB, of which 23 were superheated. No 129, the last one, was special in that it had a feed water heater.
The most of the time they were used on the Albula line. The RhB had already begun to electrify their network in 1914 and by 1919, this work was completed. Starting in 1920, seven were sold to the Ferrocarril de La Robla in Spain where they were used until around 1970. Two were sold to Brazil and with 18, the largest number came to Thailand. After their withdrawal in the sixties, the original numbers 118 and 123 are still on display in Thailand. The RhB had kept their last ones, numbers 107 and 108, as reserve locomotives which were independent of the overhead line. Both were preserved and are still in working order.
