In 1925, the Est was the first railway in Europe to get a 4-8-2 “Mountain” locomotive. This prototype, numbered 41-001, was built in the Épernay workshops to haul heavier express trains than the Pacifics, since more and more cars were built from steel instead of wood. The requirements said that it should haul 700 tonnes at 115 km/h. Designed by Émile Duchâtel, it was a four-cylinder compound with a deep and narrow Belpaire firebox. First tests showed that it produced less than 2,000 hp.