Editing GWR 2900 Class (section)

===No. 171===
A third prototype, No. 171, was built at Swindon in December 1903 (Lot 145) incorporating the improvements to No. 98 but with a {{convert|225|psi|MPa|2|abbr=on|lk=on}}  boiler and minor amendments to the heating surface and grate area. It was built as a 4-6-0 but in October 1904 it was converted to a 4-4-2 to enable better comparison with the performance of the French built de Glehn 4-4-2 Compound; it was reconverted to 4-6-0 in July 1907.<ref name="RCTS2"/> The conversion was carried out by substituting {{convert|4|ft|1+1/2|in|m|3|abbr=on}} trailing wheels with outside suspension for the final set of driving wheels. It was named ''Albion'' in 1904, renumbered 2971 in 1912, received a [[superheater|superheated]] boiler in 1910 and was withdrawn in 1946. No. 171 formed the basis of the main production series, introduced in 1905, although at this time Churchward was still unsure of the relative merits of the 4-4-2 and 4-6-0 wheel arrangements.