This is an 18th century set of sleigh bells made up of 12 marked crotal bells on a leather strap that is 44" long. They have also been called sleigh bells in songs and poems about Christmas.
Crotal bells, also known as rumble bells, were used on animals and horse drawn vehicles from the early medieval period. They have a round iron ball inside which made the bell ring when it moved. A variety of sizes were used either for fixing to collars and harnesses or fixed to the wooden frame of the wagon. 
This set of graduated crotal bells on their original strap were probably used on the horse pulling the sleigh to warn pedestrians or other sleighs of an approaching vehicle since sleighs were unable to stop in a timely manner.