A crotal bell.
Hunter ring for dog View attachment 1711832
Size does not mater in a Crotal bell. The Crotal bell is just one of many types of bells. It is also known as a rattler or rumbler because of the "pebble" on the inside of a housing that has a slit in it apposed to a hung clapper in an open bottom housing.
Crotal bells have been around since BC and used on animals to carriages and range from less than an inch to more than a few inches.
Santa’s alarm!