To be honest, if somebody had mentioned BS317 with no particular context, I wouldn't have even recognized the number as an electrical standard.
I've just checked back in the oldest A.S.E.E. guide I have, but as that relates to the 13th edition of I.E.E. Regs. (1955), it has no mention of BS317 at all.
The standard 2/5/15-amp connectors in BS546 were all in use prior to 1950, so I would assume that all were also in BS317, but as for what might have been in BS317 but not BS546 I can only take an educated guess.
One candidate might be the 2-pin (non-grounding) version of the 15A plug and socket. These were quite common in pre-war properties, but were dropped in later years. I'm not sure the exact date they ceased to be made, but it could have been as late as 1950.
