The 3571 Class was a class of ten 0-4-2T tank engines designed by George Armstrong and built at the Wolverhampton Works of the Great Western Railway in 1895-7. The 3571s, numbered 3571–3580 and built as Lot No. C3, were in essence a continuation, and conclusion, of the series of 517 Class built during Armstrong's long period of virtual autonomy at Wolverhampton. They differed from the 517s (apart from No. 1477 in rebuilt form) in that the outside frames were wider, constructed as a continuation of the valence under the running plate. They also differed in carrying larger U Class boilers with longer fireboxes than the R and S Class boilers carried by all but ten of the 517s.