On Saturday, 27 April 2019 10:35:59 UTC+1, Andy Burns wrote:
Post-1983 for 15th edition which introduced BS 4293 RCDs and pre-1992
for 16th edition 1st amendment where they became BS EN 61008, judging by
the general look of the thing, I'd say the earlier end of that range ...

Very precise, I was thinking just pre 15th Edition, but the implementation of the 15th was delayed by a few years.

Owain