Andrew Gabriel wrote:

Green protective sleeving: pre-1966.

I suspect that's a mistake. It should probably read:
Green protective sleeving: 1966-1971(?)
Green/Yellow protective sleeving: 1971(?) onwards

Agreed. Someone else posted a follow-up:

"The use of green alone as the colour identification of earthing
conductors is admissible until 31 December 1977, after which the use of
this colour may no longer be described as complying with these
Regulations." [Table B.4A 14th Ed 1976]

Non-13A socket-outlets pre-1955.

Should also add:
13A socket-outlets: post-1945 (Introduction in 1946)

Slightly later, maybe. The first edition of BS 1363 was dated 1947.
Was there a change-over date here at all? Round-pin plugs are still
allowed, after all. 1955 is the publication date of the 13th Edition,
so perhaps that's when 13 A sockets became a preferred option.

Very interesting though.

Yes.

--
Andy