This highly accomplished gourd shaped rattle is actually made from a solid chunk of a hardwood. There is a plug on the side which is where the inside was hollowed out and filled with small hard objects (seeds?) to make it into a rattle. Gourds were widely used by all classes, trasnformed into vessels, implements and many other utilitarian objects. The fact that the shape of a gourd was skillfully copied in wood suggests that it was a prestige item from a wealthy household.
See a similar wooden "bottle" published in African Furniture and Household Objects, pp. 190. The caption reads: "This bottle is a close copy of a decorated calabash."