Galvano,
That's a very nice club. It comes from Africa and an old collegue of my who worked as an accountant for the dutch government was sent to Kenia. He brought such a club back home and was very proud of it. At every occasion if you liked it or not he told about it.
Such a club was made from the roots of a tree. The end of the root was strangled by a rope and left alone for a while. Through the rope the knob developped and when it had been there for a time the root was dug up again.
The root was cut off and what left was a club like yours. It is similar to the club of that collegue of mine. He told us that the steel of the club was in the sleeve of a shirt and the knob in the hand. When necesarry the hand was opened and the club felt from the sleeve in the hand, ready for action.
I changed job, so I got lost the clubstory