After the class G1 had proved to be a good investment for its purpose, SLM was tasked with designing a similar heavier type for the main lines. There were two orders for this new class, G3, the first five engines arriving in 1892 and another eight in 1898. They were numbered 173–177 and 214–221 respectively. When all locomotives were reclassified in 1942, the G3s together with classes G5, G10 and G11 were grouped as class Sk3, all being built to the same specifications.
Typically of the period, these compound engines used saturated steam. They also had Stephenson inside valve gear with channel-type balanced slide valves. They were built as wood burners though over the years most also burnt coal from time to time. Nos.173–177 had oil lamps, but later engines were equipped with carbide gas lighting when new. Winterthur starting valves were initially fitted. The SVR began to replace these with Dultz starting valves on newer locomotives from 1907 onwards, and on older engines mainly in the 1920s.
Various modifications were made to the class. Nos. 173–177 were equipped with carbide gas lighting between 1902 and 1906. Originally these engines were normally used for goods but they later took a share of passenger and mixed-train turns as well. Trip workings, permanent way trains or yard shunting duties became their lot after the K3, K4 and K5 classes ousted them from their regular goods rosters. They found considerable use on railway construction in the 1930s and 1940s; the majority were still proving useful in the late 1950s on shunting and permanent way duties.
Nos. 173–177 were initially allocated to St Petersburg, were shedded at Viipuri from 1899 until the 1920s, and then finally based at Oulu, Iisalmi and Seinäjoki. Nos. 214–221 entered service in Viipuri while six were first allocated to Helsinki before operating out of Riihimäki, Tampere, Turku, Hanko and Seinäjoki into the 1920s. All these eight engines were finally allocated to Oulu after engineering and railway constructing duties in the 1920s and 1930s.
G3 class no. 174 was armour plated and used in battles during the 1918 Finnish Civil War. No. 173 remained on Russian territory in 1918. No. 215 was lost when sabotaged by German troops in the Lapland War of 1944. The private Rauma Railway purchased no. 174 in 1925 but it was repossessed by the VR in 1950 and its former number reinstated. The G3 class locomotives were withdrawn between 1950 and 1958.