Edwardian Diamond Engagement Ring

Hello, I am on the verge of purchasing an edwardian diamond engagement ring - 1.52 carat, VS1, transitional cut, H colour, c.1906 agreed price €11,500.

The jeweller has got a certificate from Brighton for me, however I am wondering if there is any other way of assuring its authenticity?

There is no hallmark on the ring (the jeweller said there would have been one once, which has worn off).

Is this something to be concerned about?

Also, I am wondering how noticable the H colour would be to the non-expert and is this a reasonable price for this grade of colour?

Many thanks.