For the heavy mail trains between Germany and England, which crossed the area of the Staatsspoorwegen, the locomotives of the 300 series with a 2-4-0 wheel arrangement were soon no longer sufficient to manage without double heading. Beyer, Peacock & Co. used their own designs of the 4-4-0 wheel arrangement as a basis and added a trailing axle to accommodate a longer firebox and to keep the axle load below the required 15 tons. However, the trailing axle was not radially adjustable, but only had lateral play.

Although the locomotives could reach high speeds with heavy mail trains, the running smoothness left a lot to be desired. What was even more dramatic was that they dealt damage to the superstructure and thus even had to be stored for several months. With the number 995, the bogie was moved forward by eight inches, but this did not bring a sufficient improvement. As a result, the engines were initially only used on routes with a high axle load limit and the maximum speed later had to be limited to 80 km/h. In the meantime, a superheater has been retrofitted.

No. 997 on an old color photo

When the SS and the HSM merged their vehicle fleet in 1921, the five locomotives were given the numbers 2001 to 2005. There, too, attempts were made to improve the running characteristics and the 2005 was given a series 3700 bogie. Since this also did not have the desired effect, the locomotives were transferred to goods service. Their service ended there between 1930 and 1932. Only the 2005 was converted into a brake van for measuring trains and was used in this role until 1955.