Please be aware a lot of estate, 2nd hand dealers, pawnbrokers and antique jewellery is reproduction, but sold as genuine, in bricks and mortar stores and especially on the internet.
For example only a tiny fraction of Art Deco survived the great depression, sadly the vast majority had the stones removed, so the gold could be sold. Art Deco and Art Nuevo is common especially on the internet.
I have seen a lot with reproduced English hallmarks as well. Recently cutting Diamonds in the old style has been increasing, making it more difficult for people to tell the difference.
In the 90’s as quality estate jewellery had been dropping off for years, many of these stores started buying new jewellery, To my surprise many had English hallmarks! As the masters for the copies were actual old jewellery, and the wear made them lighter (cheaper) and authentic looking. We saw this again twice in December 2016, when 2 people came in with rings they had just purchased for repairs. Like a lot of “estate” jewellery these had all the signs that they had been made in factories in Asia.