This class of rolling stock (bypassing letters "O", "P" and "Q" in the previously used scheme) presumaby indicating the use of "r" for "runner", were created in 1967 during the Marquess of Ailsa's control of the railway.  Already bad relations between the railway company and the lord were further strained when his men removed the "pairs" coach bodies from these vehicles at St. John's and left them to rot (they can be seen on photographs of the period behind the displayed locomotives) and some were dragged onto the platforms to act as passenger shelters in the following season.

Some of the underframes however were used initially to carry the former British Railways containers as part of the ill-fated “Mantainor” scheme in 1967, the remainder to be numbered 1-10 (but 10 only every carried the number in chalk as noted by J.I.C. Boyd in his extensive history of the line).  In the end, all coaches were given their “F” numbers back to all run as bogie flat wagons.