These locomotives were a development of the preceding 2-4-0Ts also by William Wakefield with the first two, No. 11 St Kevin in 1896 and No. 3 being new builds. Four more subsequently constructed by rebuilding Wakefields 2-4-0T locomotives. These were all later to form Great Southern Railways (GSR) class 428. The succeeding locomotive engineer Cronin was to build 6 more similar locomotives which were allocated GSR class 434. In practice during their lifetimes all twelve were subject to regular rebuilds with over 5 different types of boiler fitted.[2]
They were an improvement over their 2-4-0T forebears, with coal capacity up from 1.5 tons to 2.5 tons and water capacity nearly doubled to 1,500 imp gal (6,800 L; 1,800 US gal) meaning less frequent refueling. The tractive effort increase by about 2,000 lbf (8.90 kN) was also useful.[2]