hi,
to my knowledge, all tiffany diamonds regardless of carat size, come with a tiffany certificate. Diamonds greater than one carat come with the GIA certificate in addition to the tiffany certificate.
Also, each diamond has it's own registration number which should match the tiffany certificate, regardless of size.
For example, if you purchase a three stone ring, with a 1.25 center and .25 sides,
each stone would have the tiff cert. and the center stone would also have the GIA cert.
In addition to this, the newer engagement rings they sell also either have the carat weight and/or the diamond registration number inscribed within the band.
I know this because I actually went there to price diamonds (before I found Whiteflash of course).
Lastly, if you are not sure that what you are purchasing is an authentic T&co. ring, you can also request the seller to have it sent to Tiffany for formal verification and request a new letter of Valuation with current appraised value. The seller can have it arranged so the ring will be sent directly to you from Tiffany's.
As I understand it, you are concerned about an ebay purchase you won. If you are really unsure, then either do as I stated above and have the seller send it to Tiffany's, agree to meet with the seller at Tiffany's or a reputable appraiser to have it appraised before you exchange money, or tell the seller you have changed your mind. The worst thing that can happen is that you get negative feedback. No one can force you to buy anything.
I personally would prefer to purchase from a company that has a reasonable return policy, a buy back policy, and a lifetime exchange policy for full purchase price.
This way, if something doesn't check out, you can always return it. And if further down the road you decide you want a different diamond, you can always exchange it. You can't do that with an Ebay purchase.
Anyway, sorry to ramble,
Good luck with your purchase!
