Nordhausen-Wernigerode Railway No. 31 and 32

At the beginning of the 20^th century, the NWE got two 0-6-6-0T Mallet locomotives from Orenstein & Koppel which were to be more powerful than the existing 0-4-4-0T Mallets. They were introduced into service in 1910 as the first six-axle Mallets in Germany and were numbered 31 and 32. Their area of service were the Harz and Brocken lines which had tight curves and inclines of up to 3.3 percent.

The rear axles were mounted in outside frames, while the front bogie had inside frames. The central axle of each group had 15 mm of lateral play. For additional safety on the steep lines, they had a Riggenbach counter-pressure brake. The boiler with a grate of 1.9 square meters was also superheated. With an indicated output of 600 hp, they could haul 150 tonnes at 2.7 percent with 25 km/h.

In 1914, the Ferrocarril Machacamarca–Uncía in Bolivia got four locomotives of the same type which where oil-fired. After No. 32 had an accident after only ten years of service, both locomotives of the NWE were retired and refurbished to be sold to the Ferrocarril Potosí Sucre Tarabuco, also in Bolivia. Sources suggest that they were still in service in the seventies. In 2008, both could still be identified in parts at Sucre.