I know little of nothing about club type weapons (and this point was well demonstrated in my last post on one)

but looking at the difference in the patina on the end of the shaft that protrudes through the stone compared to the the rest of the shaft to it looks to me like it could have had binding on it at some point. I would think that it might originally have had a spacer in the fork with binding holding it in place, BWDIK.
Robert