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.

I have conducted a remote visual examination of this vintage rectangular black onyx signet ring. Based on the design characteristics and the warm luster of the metal, this piece appears to be 10k or 14k yellow gold, consistent with mid-to-late 20th-century American manufacture. The black onyx tablet is classic for the period, and while the inset stone is described as a diamond accent, without thermal conductivity testing, I cannot rule out a synthetic alternative like cubic zirconia or white spinel. The item displays moderate wear, particularly surface abrasions and a softened patina on the shank, which is typical for a daily-wear signet ring. In the current secondary market, vintage gold personal jewelry maintains steady value primarily due to its metal content rather than rarity. This specific design was widely produced between 1960 and 1980, making it a common but desirable 'staple' piece in the vintage market. Comparables for similar 10k gold onyx rings sold at auction or specialized vintage boutiques typically range from $400 to $700 depending on total gram weight. Limitations: This appraisal is based strictly on visual data and carries the limitation that metal purity and gemstone authenticity cannot be verified without physical testing. To provide a definitive valuation, I would require an in-person examination to verify the hallmark (karatage), a precise gram weight scale, and a diamond tester to confirm the nature of the inset stone. Furthermore, an inspection for structural integrity at the bezel-to-stone interface would be necessary to ensure the onyx is securely seated. For insurance purposes, I recommend a professional acid or XRF test to confirm the gold's fineness.