The last passenger locomotive that was still designed by the Prussian State Railways was to be able to pull heavy express and passenger trains on low mountain ranges without double-heading. The drawings were made as early as 1919 and represented the most powerful passenger locomotive of all Länderbahnen. They were put into service by the Reichsbahn and they soon became the class 39.

Like the G 12, the P 10 also got a bar frame and a Belpaire firebox. This had a trapezoidal floor plan, as it was wider at the back than the frame and lay between the coupled wheels at the front. The three cylinders each had their own valve gear, resulting in double eccentric rods on the left side. The second coupled axle was driven, but the valve gear was actuated by the third.

Sectional drawing with dimensions

Die Lokomotive, December 1923

In order to achieve sufficient running properties for the top speed of 110 km/h, the first coupled axle could be moved laterally by 35 mm and was connected to the leading axle to form a Krauss-Helmholtz bogie. The second coupled axle had weakened wheel flanges, the third could be moved by 25 mm and the fourth was fixed. Lateral play on the trailing axle was 100 mm.

The locomotives could pull 780-tonne express trains on the level or 825 tonnes at 30 km/h at one percent. However, their field of application was restricted by the fact that the axle load was more than 19 tonnes, contrary to the original plans. As a result, they could only be used on certain main routes and many locomotives had to be parked for some amount of time after their delivery. In addition, the firebox often struggled with the air supply, so that the boiler's performance could not be fully utilized.

On the Bundesbahn, the tenders were replaced with newer 2'2' T 34s with a coal capacity of ten tonnes. In order to solve the problems with the air supply, the blast pipe on 39 119 was modified. This increased boiler output by 42 percent, giving steam production of 18 tonnes per hour and a drawbar power of 2,000 hp. It is unclear whether more were rebuilt, this could possibly have affected 54 machines. They were decommissioned by 1967. The Reichsbahn reconstructed it as class 22, which received a completely new boiler.