If the ring is like the photo above, I doubt it's a true blue book (high jewelry) piece. I receive the blue books and mixed in them are collection pieces (Victoria, Soleste). Go to the Tiffany Website and look at true Blue Book collection pieces. They are very extravagant and the workmanship is amazing.
The ring above is a bit plain to me unless it is say, an Unheated 5 carat Ceylon Sapphire which then it will certainly come with papers and the owner will not lose those papers (the papers come in a nice binder).
I'm curious too about this ring and how the seller says there are only two made but has no photos of the papers or even the hallmark of the ring.
If you are going to buy a true Blue Book piece, I would insist on the seller getting a Tiffany Appraisal (not any other cheesy appraisal). Appraisals are not expensive and any authentic seller knows it absolutely confirms and adds to the value of a branded item.
Blue Book high jewelry pieces are truly one of a kind (not two). Check out the website. You can see Blue Book pieces from a few years back.
Good luck!