The slide tests 10k. I put it on a contemporary 14k gold 18" chain. Originally it wasn't a necklace/pendant. Women at the time wore long guard/watch chains, often 40–50 inches long, and this little jeweled slide would move up and down the doubled chain to hold or arrange it. A watch, locket, lorgnette, or other useful object could hang from the end. Sears advertised women’s “slide chains” in its 1897 catalog, and surviving American examples from the 1880s–1900 period use the same combination of tiny opals, seed pearls, turquoise and gold-filled construction. America had an enormous late-19th-century industry making affordable gold-filled, low-carat, and "back-and-front" jewelry, especially in places like Providence, Rhode Island and North Attleboro, Massachusetts. That industry produced huge quantities of watch chains, slides, lockets and small jeweled accessories that imitated solid-gold jewelry at a much more accessible price. These were commercially produced for the growing middle-class market. 1/4" x 3/8" pendant - it was so heavily worn that the two holes broke through with friction and became one! This is why many are "front-and-back" = more stability.