Vintage Art Deco Men's Black Onyx and Diamond Ring

This is a vintage men's signet-style ring, likely dating from the late Art Deco to early Mid-Century period (circa 1930s-1950s). The ring is constructed from a yellow gold alloy, likely 10k or 14k based on the era's common standards. It features a prominent rectangular, flat-top tablet of polished black onyx. Centered within the onyx is a white metal diamond-shaped (lozenge) setting, possibly white gold or platinum, house a single small round-cut diamond. The setting is secured by four decorative gold prongs or 'tabs' at the midpoints of the rectangular onyx face. The shoulders of the ring exhibit period-appropriate geometric engravings and stepped detailing, characteristic of Art Deco design. Regarding condition, the ring shows significant signs of wear consistent with age; there are visible surface scratches on the gold shank and the onyx tablet. The gold appears to have a slight rosy patina in recessed areas. Small nicks are visible along the edges of the onyx. No specific maker's mark is visible from this angle, but the craftsmanship suggests a mass-produced yet high-quality commercial piece from the mid-20th century.

Based on my visual examination of this Art Deco signet ring, I have assessed its value within a fair market range of $450 to $650. The piece embodies the geometric sensibilities of the 1930s-1950s, featuring a classic black onyx tablet inlaid with a white metal lozenge and a single round-cut diamond. The 10k or 14k yellow gold shank displays characteristic stepped shoulders and period-appropriate engraving. The condition is consistent with an antique piece that has seen regular wear; the 'flea bites' and surface abrasions on the onyx, along with the patina and scratches on the shank, indicate its age but detract slightly from its 'mint' investment potential. The market for mid-century men's jewelry remains steady, particularly for iconic styles like the black onyx signet, which appeals to both vintage collectors and contemporary wardrobe enthusiasts. The item is assessed as a high-quality commercial piece rather than a bespoke artisan creation. However, definitive valuation is limited by the digital nature of this inspection. A physical examination is required to verify the gold purity via acid or XRF testing, confirm the diamond's clarity and color grade, and check for interior hallmarks that could link the piece to a specific maker (such as Ostby & Barton or Belais), which could increase its rarity. Without a physical loupe inspection, I cannot rule out the possibility of synthetics or determine if the diamond is a later replacement.