A small (a bit more than 1 inch high) cage crinoline pendant, c. 1863-1868.
These crinolines (or hoopskirts) were worn under dresses, to provide the desired elliptical, off-center appearance for gowns of that time.
The small loop at the top with an inner diameter of 3.2mm allows a chain, ribbon or leather cord to be pulled through so that you can wear the crinoline as a pendant or charm on a bracelet.
I have more undergarment jewelry from various periods in my shop!