CP 553 is one of the most imposing locomotives in the collection. It was acquired in 1924 by the Southern and South-eastern Railways, as part of the reparations due to the Allies after the First World War. Being one of the largest steam locomotives, it could haul 400-ton trains, reaching a speed of 120km/h. In 1927, it was deployed on passenger, goods or mixed services on the Northern mainline, with emphasis on Lisbon-Porto fast trains. In the 1940s, some locomotives were adapted to burn fuel oil, and along with reinforcement of bridges and viaducts in the south of the country, this allowed more frequent use to Vila Real de Santo António. Sometimes, they also hauled the Algarve Rapid Train, the most emblematic service on the line and of this series of locomotives. The introduction of diesel locomotives would dictate their substitution on these services and they were withdrawn in the 1970s. They would be known on the railway as the