that is a gear from a piece of machinery, looks like a bit from a car differential, makes a nasty mace doesn't it!
BMW 2002 differential bevel gear: (unfortunately broken)
reminds me of the ww1 trench mace head that was supplied to slip onto the handle of the issue entrenching tool in lieu of the shovel/pick head.
here's mine fitted onto a replacement handle:
would definitely ruin your day to be thunked with either. yours is prettier tho.