The Caledonian Railway 55 Class were 4-6-0 mixed-traffic locomotives designed by John F. McIntosh and built at the railway’s St. Rollox works in Glasgow in 1902-1905. The class was intended for use on the Callander and Oban line and were sometimes known as Oban Bogies, a nickname they shared with the earlier Brittain 179 Class 4-4-0s and the subsequent Pickersgill 191 Class 4-6-0s, all of which were built for use on the same route.