The twenty examples of this class were designed by Patrick Stirling for the GSWR and were built by Sharp Stewart and Company (Works Nos. 1196-1205, 1264–73 and 1359–60) between July 1860 and October 1862. They were numbered 23, 35, 37, 116-122, 22, 24, and 123-30. The members of the class were fitted with domeless boilers and safety valves over the firebox, these were later replaced by those of Ramsbottom design over the centre of the boiler following a boiler explosion at Springhill in 1876. The original weather boards were also replaced by Stirling cabs. Eight of the class were rebuilt as 0-4-2T locomotives between 1880-1886.
The unrebuilt locomotives were withdrawn by Hugh Smellie between 1882 and 1888. The rebuilt locomotives were withdrawn between 1890 and 1904.
- Baxter, Bertram (1984). Baxter, David (ed.). British locomotive catalogue 1825-1923, volume 4: Scottish and remaining English Companies in the LMS Group. Buxton: Moorland Publishing. ISBN 0-903485-53-2. OCLC 59913101. OL 25432141M.