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+3⁄4 inches or 7 cm across, with anything between 3 and 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 has been produced to explain their use or significance, with none gaining very wide acceptance.
They are not to be confused with the much larger smooth round stone spheres of Costa Rica.
Marshall-1976-1977
was invoked but never defined (see the help page).