Short answer — these are the jewelry names most clearly tied to Taylor Swift’s engagement (announcement: August 26, 2025):

• Artifex Fine Jewelry — the ring was designed by Kindred Lubeck of Artifex (credited by Swift’s team and widely reported). (apnews.com)
• Kindred Lubeck — the individual goldsmith/designer who co‑designed the custom Old‑Mine/old‑mine‑brilliant style diamond ring. (apnews.com)
• Signet Jewelers — mentioned in market coverage because Signet’s stock briefly rose after the engagement photos of Swift’s cushion/old‑mine‑style ring circulated. (cnbc.com)
• Steven Singer Jewelers (Philadelphia) — not the maker of Swift’s ring, but the shop publicly offered a $1M, 7½‑carat ring to Travis Kelce earlier (Jan 2024) and has been repeatedly linked in coverage. (inquirer.com)
• Cartier — Taylor was pictured wearing a Cartier diamond‑encrusted watch in the engagement announcement photos, so the brand was noted in coverage of the post. (apnews.com)

If you want, I can pull up the original announcement photos/articles or show a short timeline of when each brand was reported.