I found a wooden jewelry box from a local second-hand market. There are about a dozen rings inside. These rings are made of copper and can be adjusted.
There are some words on the rings. After asking a professor, I learned their meanings. “福” is good luck; “富贵” is wealth. People who believe in feng shui like to wear it.
Due to too much time, the surface of the rings have been oxidized and turned black.
If you are interested in it, you can take one for $78 (free shipping).
Note: Only a small amount was left. If necessary, quickly!