39-831 BR MK1 FO First Open BR (SR) GreenThe British Railways Mk1 was the designation given to BRs first standard design of main line coaching stock, and one of its most successful. Built from 1951 until the early 1960s to augment and replace the array of Big Four and earlier pre grouping designs inherited from the LMS, LNER, GWR and SR, BR took the best features from several of these types to produce the new steel bodied design. As a result, the Mk1 was stronger and safer than any of the