UK traffic sign- Plate for use with sign in diagram 501  diagram 502 (TSRGDNO 502), with dimensions.; This is a deprecated design or diagram, reconstructed from anlaysis of the 1981 Schedule, and the 2002 era working drawings. It may not be wholly accurate.
Traffic Signs Regulations and General Directions 1981; Working drawings for Traffic Signs -  [1] namely the Alphabet Working Drawings here [2]

, and extrapolation of details thereof.; Redrawn by uploader
Department for Transport (United Kingdom); Redrawn by uploader