As a successor to the class 4 and 5 express locomotives, Karl Gölsdorf designed the class 6, which was his first express locomotive. Like its predecessors, it also had two driving and carrying axles each. In order to achieve the required increase in output, Gölsdorf took a different approach to arranging the boiler, which was inspired by the famous number 999 of the Pennsylvania Railroad, among others.

Instead of arranging the boiler very low, as was previously the case, to achieve the smoothest possible running, a boiler with a larger diameter was used here, with the firebox standing completely above the frame. Thus, a continuous output of up to 900 hp could be achieved through a larger grate and evaporation surface. In addition, it had a two-cylinder compound engine with the high-pressure cylinder on the right side.

A total of 68 were built between 1894 and 1898, which reached speeds of up to 130 km/h in test runs. Nevertheless, approval was only granted for a speed of 90 km/h, which was sufficient in Austria. The BBÖ still had 20 in service after the First World War and used them until 1932. 28 were in service with the ČSD until 1938 as class 264.0 and nine more with the PKP as Pd12.