antique one cannot possibly be 'certificated'.
You should be able to pick up antique one at well below 'valuation' price.
To find out if clarity/colour/carat/cut (the 4 c's) is right, how about buyig the ring, but doing a deal with seler, that if the intended receipient is nto happy with it, a FULL refund wil lbe given.
that gives you time to get it appraised in another jewellers.
If you are then happy, SHE has accepted, if you are not happy with valuation and appraisal, SHE is not happy, and you get the full refund.,