We are not jewelers and we are not experts but we have a good inventory of gold marked jewelry with semi precious stones. We use a diamond tester and have a gold kit. This one came from a large expansive and expensive jewelry estate. 19 inch 10 kt gold chain is marked... weighs 3.8 grams total THL & DO ...The THL is the trademark of Samuel Aaron, Inc., who is a jewelry designer. . the stone in centre is a ruby and there is a circle of white stones that did not test as diamonds and estimate they are topaz stones. Nice long gold chain and pendant. will be shipped tracked mail. inv 11 2020 This gold jewelry item comes in the padded white vinyl box shown 3 2024.