I saw this 1820s citrine locket ring on ebay and that it looked to be my size and since it was reasonably priced, I couldn't resist! I got it yesterday and it fits perfectly! I'm so excited! The dealer seemed reputable, though I know you're always taking a little bit of a chance. And I'm no expert. Here are all the details.
From the auction: "A citrine stone has a surround of pearls to create this ring. There is leaf and scroll decoration to each shoulder. There is a locket to the back with the original glass present. The ring is made in 18 carat yellow gold. The design and craftsmanship date this ring to the Georgian period, circa 1820. The stones and setting is 9mm by 9mm or 0.35 inches. Weight is 2.2g or 0.08oz. American size 7 3/4
. Internal circumference 56mm."
And the auction pics: