Tiffany & Co Engagement Ring

I'm selling my Tiffany & Co engagement ring, purchased from the flagship New York store, 0.84 carats, classic six prong setting in platinum. Size 6.5, but can be resized. Ring was worn for less than a few months, in perfect condition, we're just going to get an upgrade. Comes with ring box, folder, diamond certificate, and insurance certificate. Asking $10,000, new from Tiffany's approximately $18,000 (https://www.tiffany.ca/engagement/engagement-rings/the-tiffany-setting-engagement-ring-in-platinum-GRP10862/the-tiffany-setting-engagement-ring-in-platinum-73100097/)