The London Midland and Scottish Railway (LMS) Rebuilt Royal Scot Class is a class of 4-6-0 steam locomotives. 70 members of this class were rebuilt by the LMS and its successor British Railways (BR) from LMS Royal Scot Class engines by the replacement of their life expired parallel boilers with a type 2A boiler over the period 1943-1955. http://en.wikipedia.org/wiki/LMS_Rebuilt_Royal_Scot_Class