After the first type A 3/5 express locomotives, the Gotthardbahn had Maffei develop another variant of this type in 1908. Although it was primarily intended for use on the company's valley routes, it was also intended to pull lighter trains on the mountain routes and, like its predecessors, was therefore given relatively small wheels with a diameter of 1,610 mm. Maffei used the basic construction of the Bavarian P 3/5 as a basis.

Thus, the locomotives had a bar frame and a long, narrow firebox that lay between the wheels of the second and third coupled axle. The roof of the firebox sloped backwards so that it was always sufficiently covered with water when driving downhill on the 2.7 percent mountain route. To increase efficiency, a Crawford-Clench design steam dryer was used, which was replaced by the Schmidt smoke tube superheater from 1913 onwards.

The dimensions of the cylinders and parts of the valve gear corresponded to the type C 4/5 freight locomotive also supplied by Maffei in 1906 in order to reduce the number of spare parts to be kept on hand. All cylinders acted on the first coupled axle according to the Von Borries design. A piston valve was used on each side, which simultaneously controlled one high- and one low-pressure cylinder. While this arrangement was efficient, over time it resulted in damage to the valve gear.

Sectional drawing with dimensions

Die Lokomotive, June 1909

Maffei delivered four vehicles, four more were delivered by SLM in Winterthur in the same year. On the valley lines, they could transport 350-tonne trains at one percent at 60 km/h, and at 2.7 percent on the mountain route, it was still 150 tonnes at 40 km/h. The Gotthard railway was nationalized as early as 1909, so that the locomotives were now operated by the SBB. After the Gotthard Railway was electrified, it was scrapped as early as 1925.