Wow. So, I can''t really breathe right now! Just stumbled across (through the wonders of google image search) www.sjphillips.com whose thing is apparently jewelry that makes my heart stop beating!
First, I fell in love with this 7.41ct beauty, helpfully color coded as "over 40,000 pounds"
My jaw-popper is 20-40,000 pounds & genuine Tiffany.
ETA: Art Deco diamond and onyx ring by Tiffany, New York c.1920, collet set brilliant cut diamond, approximately 2.00cts, to a square onyx plaque with rounded corners, French cut diamond set shoulders, engraved and pierced gallery and mount