Art Deco style marquise ring (not authenticated)

This piece appears to be an Art Deco style cocktail ring featuring a prominent marquise-cut or navette-shaped deep blue central stone, likely glass, synthetic spinel, or synthetic sapphire, though gemological testing would be required to determine its exact material. The mounting displays elaborate silver-toned metalwork, possibly white gold, platinum, or sterling silver, styled with intricate milgrain detailing, geometric patterns, and openwork filigree surrounding the central gemstone. The elongated cluster design is characteristic of vintage costume or fine jewelry from the early-to-mid 20th century. Visible condition indicators show minor surface wear, tarnish, and slight softening of the delicate metal details under magnification, consistent with age and handling. There are no clearly visible maker's marks, hallmarks, or signatures apparent in this photograph, so the identification rests entirely upon stylistic elements such as the marquise silhouette, geometric bezel, and textured shoulders. The overall craftsmanship suggests either a period piece from the Art Deco era or a later revival creation designed to emulate that distinctive aesthetic. The item is unauthenticated and presented purely on visual characteristics.

Based on what I can see in the photograph, this item presents as an Art Deco style cocktail ring featuring a prominent marquise-cut deep blue stone surrounded by intricate openwork filigree and milgrain detailing. However, photographic analysis has significant limitations. I cannot determine the exact material composition from an image; the central stone could be synthetic sapphire, synthetic spinel, or colored glass, while the metal mounting could be sterling silver, a base metal alloy, or low-karat white gold. There are no legible hallmarks visible to provide guidance on purity or maker. Visible signs of minor surface wear and patina align with vintage age or handling, but a physical inspection is essential to test the metal with acid or XRF analysis and to conduct gemological testing on the gemstone. In the secondary market, vintage costume or silver Art Deco revival rings of this style typically realize between $75 and $150. If physical testing were to reveal that the mounting is platinum or 18k white gold housing a natural, untreated blue sapphire, the value could increase substantially into the four-figure range. Conversely, if it is a modern base-metal costume reproduction, the fair market value would realistically sit closer to $20 to $40. Therefore, the estimate is offered as an unauthenticated working hypothesis.