An elongated oval of pink-red topaz, cut as a cabochon so it reads as colour rather than as facets, bezelled in white gold with carved leaves running out along the shoulders in yellow.
Red stones in vintage jewellery are nearly always ruby or garnet, and both of those run dark. Topaz this colour stays bright, and against a cool white bezel it goes brighter still. She is an old ring that does not look like one, which is rarer than it sounds.