When the Pfalzbahn wanted to try out new ways of temporarily increasing the tractive effort of express locomotives, they ordered a locomotive from Krauss that was called “Dr. von Clemm”. Here a Helmholtz patent was used, which Kraus had already used on the Bavarian AA I and which provided for an additional, lowerable axle with an additional steam engine. While the basic construction of the AA I corresponded to the wheel arrangement 4-2-2 and where the additional axle was installed in front of the coupled axle in the frame, the P 3II was a 4-4-2 (Atlantic), in which the additional axle was placed in the centre of the bogie.