Read Carved stone balls (Wikipedia)

Carved stone balls are petrospheres dated from the late Neolithic to possibly as late as the Iron Age mainly found in Scotland, but also elsewhere in Britain and Ireland. They are usually round and rarely oval, and of fairly uniform size at around 2.75 inches or 7 cm across, with 3 to 160 protruding knobs on the surface. They range from having no ornamentation (apart from the knobs) to extensive and highly varied engraved patterns.[2] A wide range of theories have been produced to explain their use or significance, with none gaining very wide acceptance.