See photos for makers hallmark. There are 5 stamps on the metal (photo 3, small ring left side) but they are too small to read without a loop. Purchased from a reputable UK retail jewelry store either Beaverbrooks or Chisholm Hunter, can’t remember which one. - C - C = 2002 - W375W - Stamped 375 = 9K gold - Anchor = Birmingham Assay Office 16” curb chain. Height 1mm; Width 1/16th of an inch or 1.5mm (see photo, also added a Google image as reference to show thickness compared to other size chains) Chain very dainty with small tight links that shimmer subtly in the light. Good quality - very sturdy. 9K chain has a “champagne” color due to lower gold content. Side by side comparison: 24K is the brightest yellow/orange; 14K will look lighter/yellow; and 9K will look light but more “brassy” than the 14K. I do not know the alloys of this 9K chain Please reach out with questions before purchasing, no returns accepted