I just realized there's a Great Britain forum.
Yep. I just moved this thread there.
Confirming the date ranges: 1919 and earlier are sterling silver (.925 fine), 1920-1946 are .500 fine, 1947-1970 are cupronickel.
So, would a 50% one still turn my finger green?
Don't know about your finger, but the ring itself might. .500 fine silver can look a bit coppery, and is more prone to verdigris than finer silver.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis