I believe this to actually be more than just a charm. Because of the four small holes in the top, it is very possible this is what's known as a Flea Catcher. They where prevalent in the early eighteen hundreds. One would place body oils or hair inside. This would in turn attract fleas to enter and become stuck and die. This is silver but has no markings. It does not open but is in two pieces only held together by the wire going through attached at top by a ring.
Measures 7/8 x 1/2 inch.