Set of 3 Decorative African Balls

Set of Decorative African Balls. I believe that they are made of wood and Ivory with brass accents. The large one is 5 1/2” across with a circumference of 15”. The middle size is 4” across with a circumference of 12”. The small one is 3 1/2” across with a circumference of 9 1/2”. They are fairly heavy.