Vintage Black Onyx and Diamond Accent Rectangular Signet Ring

This is a vintage-style signet ring featuring a rectangular face composed of a polished black onyx tablet inset with a single small, round brilliant-cut gemstone, likely a diamond or cubic zirconia, in a four-prong or star-style setting located in the lower portion of the stone. The ring is constructed from a yellow-toned metal, typically 10k or 14k gold, characteristic of mid-20th-century design. The band is a tapered, polished shank that broadens as it meets the rectangular bezel. Measuring approximately 15mm in vertical height on the face, the onyx exhibits a smooth, reflective surface with deep black opacity. Notable condition issues include visible surface abrasions and fine scratches on the yellow metal bezel and shank, consistent with moderate wear and age. The metal shows a warm patina overall. The craftsmanship is indicative of mass-produced fine jewelry from the 1960s to 1980s, often used as men’s or unisex fashion rings. While no hallmark is visible in the photograph, the style and heft suggest a gold-fill or solid gold composition rather than a gold-plated base metal.