Sterling natural gemstone ring*lowest

Vintage piece. Has a chip on one side of the stone. Pictured. Can be buffed. I’m unsure what the gemstone is, but it feels natural. There are TINY clear stones in the top sterling setting. I’m betting they’re diamonds due to the size and setting. Hallmarksd RSE. Stamped 925. Fits my ring finger . So about a size 4-41/4