The majority of responses recommend getting multiple independent certificates and appraisals. Either two grading certificates, a grading certificate and a valuation certificate, two grading certificates AND a valuation certificate. The combinations go on.
If a retailer is offering you multiple independent certificates and / or valuations, accept them but always ensure that you know where they come from and that they are independent.
Now, you have multiple documents stating the characteristics of the diamond. But the question still stands! “How do I know that the diamond I am looking at is the same one revered to in the certificates?”
There are really only two ways to confirm that the diamond matches the certificate.
The first method is to compare the diamond (under magnification) to the plotting on the grading certificate. All internationally recognized grading certificates should have a plotting of the stone. The plotting shows the diamonds internal flaws and external blemishes.
This method though, can be difficult to the untrained eye, depending on the clarity of the diamond.
The second method is to ensure that the diamonds you are looking at are laser inscribed.
“Laser inscription is the use of a very fine, precise laser beam to write a grading report number or customised personal message on the girdle (outside perimeter) of a diamond. The laser inscription is totally invisible to the naked eye and can only be seen with a magnifying loupe. If done with a cold laser, it does not change the colour or clarity grade of a diamond and is considered permanent as it can only be removed by a professional diamond cutter.”
DCLA Laser inscription service description [http://www.dcla.com.au/services_inscription.htm]
The permanent laser inscription enables you to check the authenticity of a diamond at any time. The inscription is usually easily visible under a 10x jewellers loupe.
The process for having a diamond laser inscribed further ensures this safeguard. Laboratories working to international standards will not simply inscribe any certificate number onto a diamond. The diamond must first pass a verification test to ensure that the grading certificate is authentic and the diamond matches the certificate. Only then will that certificate number be laser inscribed onto the diamond.