On Friday, 3 May 2019 16:30:16 UTC+1, wrote:
Looking round a house (with a kitchen refit done in 2013 and a
boiler in 2010...) and came across some bare wire earths
https://flic.kr/p/2fGbsTq

Very new service head and meter on a delightful old board ...

I think bare earths are pre 1966. Green earths 1966-77 (although not always sleeved inside back boxes etc).

Owain