French artisan ring with purple stone

Artisan ring from a small boutique in Paris, France (I can’t remember if it was on île Saint-Louis or on Île de la Cité). Circa: 2011. Most probably solid .925 Sterling Silver, but the artisans in France are not required to stamp .925 or the official French hallmark for Sterling silver if the piece weigh less than 30g. The maker’s mark (poinçon de maître), as seen on pictures, is a solid guarantee, though, but the ring is priced lower here because we like our silver sterling hallmarks, in North America... ! Construction: Hand-crafted tulip/corolla basket setting featuring a closed-back gallery. The smooth, solid band shows a subtle, organically rounded contour and slight texture, indicative of artisanal lost-wax casting or manual polishing. Gem Type: High-grade Synthetic Amethyst (or premium Purple Cubic Zirconia). I thought, when I bought the ring in 2011, that it was an amethyst, even if it was not specified, but now I don’t think it’s genuine, as it is substantial and too clear for the price I paid in 2011 (100 euros / 160 $). Color: Deep royal purple with subtle indigo and violet flashes under natural light. *Condition: Very good estate condition. No visible oxidation or tarnish on the metal, and no visible scratches on the stone. The irregularities seen on the band are part of the artisan work and normal wear. *Size: I think it is a size 5 or slightly smaller (4,75 ?), as I usually wear sizes 4,75 and 5. See pictures for the size and compare with one of your rings.