RR.X from installation to rebuilding, 1922-1950. The cars kept the odd ventilators used on previous truss rod classes.
All subsequent classes use normal hatches, although opening opposite of other roads.
RR.X retained the roof clips of RR.W but used the smaller herald. As with RR.W the cars were rebuilt with steel superstructures beginning in 1936. However, the program took until 1950 to complete. Kit 8602 covers class RR.X cars in all physical and lettering styles from delivery to rebuilding.