Designer Engagement Ring - Diamond In The Rough; NYC

This is an 18K gold, Diamond engagement ring; it was made by Diamond in the Rough - a Custom Jewlery Designer located in New York City. https://ditrjewelry.com/ The band is 18K white gold and the center diamond is 0.96ct rough cut diamond. The inner band is stamped with "750, 0.96" The design is called "Modern Champagne Yellow Raw Ring" - and I purchased it at the time for $3,000. A nearly identical version can be found here: https://ditrjewelry.com/collections/modern/products/copy-of-0-96ct-minimalist-18k-uncut-lemon-yellow-engagement-ring?variant=37001819553957 The ring is stamped with their Hallmark. I am the only owner of the ring, and I purchased it directly from the designer in 2012. The ring was unworn as I did not proceed with the proposal and it just sat in my closet for over 13 years in its case. Over the years, I did misplace the original paperwork and receipts but I can likely reach-out to the designer and secure documents if necessary.