The S 2/6 was a one-off that was only intended for testing higher speeds. It was ordered in December 1905 and developed and built within just four months. In terms of wheel arrangement and driving wheel diameter, it corresponds to the Prussian test locomotive S 9, with which high-speed tests had been undertaken shortly before. In contrast to this, however, the S 2/6 was otherwise based on near-series technologies.
In addition to the two coupled wheel sets with 2,200 mm wheels, the measures used in various places to reduce air resistance are distinguishing features of the locomotive. Other express locomotives of the time also had a cone-shaped smokebox door and a driver's cab tapered at the front, but there was a smooth transition from the boiler to the driver's cab. The streamlined cladding of the chimney, steam dome and cylinders went even further.
With a large grate area compared to other locomotives, a very good evaporation performance was obtained. Together with the four-cylinder compound engine, a calculated indicated output of up to 2,200 hp was achieved during test drives. On July 2, 1907, with four wagons with a total weight of 150 tonnes it traveled at a speed of 154.5 km/h. This value was a world record and caused a stir internationally.
Immediately after the test runs, the S 2/6 was put into regular use, where it was able to reach a speed of 120 km/h with trains weighing 360 tonnes. In operation in Bavaria, it was particularly unpopular with the planning staff because it was a one-off and its characteristics differed greatly from the other locomotives used. Compared to the S 3/6, the S 2/6 had more power, but with only two coupled axles it could generate less traction, which made planning the simultaneous use of both locomotives very difficult.
In 1910 the locomotive was relocated to the Palatinate network, which belonged to Bavaria, and was more popular there. On the Reichsbahn it would have become class 15, in which it would have been the only locomotive with a 4-4-4 wheel arrangement. However, after returning to Bavaria, it was decommissioned, refurbished and taken to the Nuremberg Transport Museum in 1925, where it is to this day.