As mentioned, I don't know a great deal about SSHRs, but this one is a beauty. Personally, I believe that the comments you have received here and on the WRF should suffice as pretty strong confirmation of your ring's authenticity.
As I understand, so-called 'Certificates of Authenticity' from certain individuals are no longer worth the paper they are written on. My advice is, don't waste your money paying for a dubious piece of paper that you don't need.
Stephen
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