In 1939, the Belgian State Railways ordered Cockerill to build six streamlined Atlantics to speed up express trains between Brussels and Ostend. While this wheel arrangement was already unusual at the time, the inside cylinders with outside valve gear were also unusual. With a maximum permitted speed of 140 km/h, trial runs reached 165 km/h, while the trains often exceeded an average of more than 110 km/h. Average speeds of 120.46 km/h from station to station were also achieved, which is still the European record for steam trains to this day. When the route for which the locomotives were built was electrified, they were used on other routes. They were decommissioned by 1962 and road number 12 004 is now in the “Train World” in Schaerbeek. 