The bells in Saturn and His Children are called crotal (rumbler or pellet) bells. As defined by the UK Detector Finds Database:
...its clapper is loose and contained within an enclosed chamber with perforations to allow transmission of the sound.These types of bells were made of either pewter or copper alloy. Most of the period representations that I've been able to find for crotal bells appear to be from England, but obviously this design was also used at least in the later centuries in the Germanic countries. These small bells, it is claimed, were originally cast using the lost wax method.
Metal Detecting Holiday in England
Florilegium Article on Bells