The first was delivered in May 1896 by Beyer, Peacock and Company with further orders over the next 20 years seeing the class number 280. Their second and third coupled wheel tyres were flangeless to reduce curve friction.
The last 75 were built with superheaters and after being judged a success many of the class were retrofitted. Many of the class received turret type tenders in later years which provided better visibility when operating in reverse.
In the 1930s 72 were withdrawn and after being used during the load testing of the Sydney Harbour Bridge in 1932 with most of these locomotives being latter scrapped, although 14 were rebuilt with superheaters and returned to service. By mid-1964 there were only 113 left in service with the class by now normally restricted to working coal trains in the Hunter Valley and shunting duties in the larger marshalling yards throughout the system.
5069 and 5132, both preserved at Dorrigo, were 2 of the 88 locomotives used to test the Sydney Harbour Bridge before it opened. 5132 is the only superheated 50 class preserved and it is fitted with the only preserved Mort's Dock tender. 5069 is stored in operational condition.