Dorothy Marshall has extensively studied these objects
(http://minerva.york.ac.uk/catalogue/proj_data5/PSAS_2002/pdf/vol_108/108_040_072.pdf; http://minerva.york.ac.uk/catalogue/proj_data5/PSAS_2002/pdf/vol_113/113_628_630.pdf).

But makes the following observations:
1. Size and weight seems uniform - a standard weight? Primitive societies are greately concerned with issues of fair exchange. But weighing what?
2. The objects are virtually unchipped, inspite of being portable objects. This makes it unlikely that they were used in throwing games or as weapons.
3. They are not of a suitable form to be attached to sticks as mace heads.
4. Some show suggestions of polishing around the waists of the knobbles - kept in strings bags?
5. Another suggestion is a sort of conch - where only the holder is allowed to speak - this makes sense to me, as the similarity of the communiuty set-up often reminf me of some rural African societies with their village chiefs/elders dressed in their regalia and surrounded by 'ritual objects'.

Marshall, however, concludes that these objects function is wholey unknown!

Tim Bucktoo