In the olden days, such rings were worn by men and women and served useful purposes, if not for just to store precious locks of hair, messages, or holy relics. Read my article on their history here.
Perhaps compartment rings are still used today in covert operations or in old-fashioned corners of the world (imagine an aging countess looking for a way to "influence" the outcome of a family matter). Maybe this notion is a bit too Hollywood, but it's fun to conjure images of nefarious plots that involve the least suspicious character slipping something odorless and tasteless into a glass of wine with a simple tip of the ring.
The vessel ring pictured above has an amethyst on top. I love amethysts and other colorful gemstones. There are some minerals that are really more rare than diamonds and are a better investment, because as we know DeBeers controls the diamond market. If their hoard were ever to flood the market, the price of diamonds would go way down, because white diamonds (mined and unmined) are actually quite abundant.
I have a more vivid memory of accidentally bumping my forehead on a spotless glass pane at the St. Louis Galleria mall, where a shop had a very nice Hope Diamond replica on display in their front window. That's what I get for being so enthusiastic about gemstones.