Re-using the bogie underframes from “pairs” carriage F.50 (which consisted of four-wheelers B.7 and B.8) the carriage bodies were removed at St. John’s Station in 1968 and discarded in the yard, later scrapped on site.  The underframes became the final of the series, R.12 (though some sources state there was a thirteenth such runner for which there is no supporting evident).  This was notable in only carrying its non-canonical fleet number in chalk.  The frames were later changed back to their original fleet number F.50 and in this form it remains on the railway today.  Today, this runner carries both F.50 and F.64 lettering further compounding the riddle of this series!