When I was searching I too came across a GIA report with a 1999 dated certificate.On inquiring as to whether this stone was being resold I was told by a vendor that it is sometimes normal for a diamond to sit in inventory for that long and not be sold. I was also told that they would inform me if it was indeed being resold.
I can't explain why but I didn't completely buy that theory. However I also didnt have any evidence to suggest otherwise either. Also know that if a diamond is indeed being resold more often than not, the vendor makes a larger profit on it.
That is true, sometimes a diamond can sit in inventory that long. But with saying that I would ask myself why. Did the store pay too much, did they buy something that went our of style in their area, is it graded properly? Or is it a resale?
Some jewelers will submitt the diamond again if the date looks rather old and get a current grading report. If the diamond is old enough they will recoupe the grading fee(and more) by the increase in diamond prices over the years.
I have a couple oldies too, I just stopped selling ovals for some reason
I did take what I could and used them in three stone rings and those then moved
Oh, if I could buy some older diamonds graded in the 70's I would buy most of those real quick. I used to see SI1's that look better than many VS1's today.
This is another issue, but I think the grading is not as tight as it was 30 years ago.
My fear with an older stone grading is that being in the market so long and being passed up, it could have been handled a few times, etc... Who knows if there have been any nicks, abrasions or damage done to the stone either by trying to unsuccessfully set it, or even just movement from jeweler to cutomer, and back, etc...
I would have them regrade the stone to ensure that the report is up to date and reflecs the stone as it is now...