4S-517-003 OO Gauge 1158 GW Green Open CabLocomotive background Information The 517 Class were small 0 4 2T tank engines designed by George Armstrong for local passenger work on the Great Western Railway. 144 were built at Wolverhampton Works in 13 lots and were outshopped between 1868 and 1885. During the late 1880s and early 1890s most had their wheelbases lengthened to 15 foot 6 inches and from 1904 onwards several were converted to auto train working which scattered them over the system.