A vintage yellow gold signet ring featuring an oval black onyx and a central diamond. Product details: Materials: The ring band is crafted from 9-karat (375) yellow gold. Inlay: A smooth, polished oval of natural black onyx. Centerpiece: A small round diamond—featuring either a classic or simplified cut—is set within a small, diamond-shaped (or star-shaped) platinum or white gold plaque at the very center of the onyx. The design reflects the retro/mid-century style (mid-20th century; such models were particularly popular from the 1960s to the 1980s). Jewelry of this type is considered versatile and was frequently worn both as men's signet rings and as unisex accessories.