[Closed] Any jewellery/hallmark experts in?

Looking at buying a 'vintage' emerald/diamond ring and I've been trying to check the hallmark; however, I have encountered some difficulties: the age letter would suggest 1950 as it's slightly worn it's hard to tell as the 2014 mark is similar (though thinner in parts on a clean mark).

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https://flic.kr/p/25RdqrJ

However the fineness mark (750) is proceeded by a crown which from my research suggests 1975-1998 as pre 1975 would have been a crown and [18]  from: 

Item also has a modern laser engraved stone weight which suggests either it is modern or has been resold/valued in modern times and has been re-marked.

https://flic.kr/p/25RdqsW

Any experts in the house?  Thanks.