This class of locomotive was designed by the New South Wales Government Railways as a modification of the earlier T(524)-class, after 1924 classified 50-class. All the coupled wheels had flanges and a certain amount of side movement was given to the middle pairs with a laterally operating knuckle joint being provided in the middle section of the coupling rods. The Clyde Engineering Company delivered the first locomotive in April, 1912 and, by November, 1917, a total of 190 were in service, 160 from Clyde and 30 from the NSWGR Eveleigh Workshops. Most were fitted with superheaters when built and some fitted at a later date. The superheaters caused some initial difficulties, giving the class a bad name. Because there were so many locomotives built, their numbers extended into the 5400s, meaning there was no technical 54 class of locomotives. There was also a problem with the locomotives being unbalanced, causing speed restrictions to be imposed to avoid rough riding and track damage. Following further investigations, 24 of the class were re-balanced and these were permitted to operate at a faster speed which made them useful on Wollongong suburban passenger services. When introduced, most of the class were fitted with a standard bogie tender, similar as those attached to the 50-class, although some saw service with Wampu tenders. In the later period of their lives, the majority were fitted with larger turret type tenders. To enable tender first running, many had automatic couplers fitted to the front. Following the removal of the knuckle joints from the coupling rods, flanges from the second coupled and driving wheels and the fitting of boilers standard for 50-class; 53-class and 55-class, they became most useful locomotives. Many were in service right to the end of the steam era, four surviving to the very last day. The then Commonwealth Railways used the design of these locomotives for their KA-class for the Trans-Australian Railway.
5461 was selected for preservation by the New South Wales Rail Transport Museum and is currently displayed with a WAMPU Tender at their Valley Heights museum. 5353 is preserved by the Dorrigo Steam Railway and Museum. 5367 was preserved by the Lachlan Valley Railway, and after providing many years of sterling service to the group is the subject of an attempt to return it to steam