The Swiss Federal Railways (SBB) purchased two new class HG 3/3 cogwheel locomotives for their Brünig line starting in 1905. They were delivered by SLM Winterthur. After both prototypes had given good results, 17 of these locomotives were placed into service by 1910. Another locomotive was subsequently delivered in 1926. One of the biggest advantages of these 30 metric ton locomotives – in addition to the higher performance of 400 horsepower and the greater maximum speed of 40 km/h / 25 mph in adhesion operation and 13 km/h / 8 mph in cogwheel operation – was the fact that they could also run downgrade with the smoke box in front. This did away with the need for time-consuming switching and turning of the locomotive at the summit of the pass at Brünig. After electrification of the Brünig Line in 1941, these steam locomotives were no longer needed for regular service. Part of them did however remain operational in reserve, the final units being road numbers 1065, 1067, and 1068. They were finally retired in 1965. Road number 1067 then went to the Ballenberg Steam Railroad, where it has been used since 1972 for nostalgia runs on the Brünig Line, together with the passenger cars, car numbers BC 28, and C 31, and the baggage car, car number F 51. Since January 1, 2022, the name of this museum railroad has been Brünig Steam Railroad BDB.