Iron? Brass? Both ends hollow? Is it broken? What is the diameter? Is the slot on both sides? Need more info...
DCMatt

I know this doesn’t help much.
I have seen a lot of handles of different kinds of jacks and hand pumps that had that kind of a slot cut into it, but the handles are hollow all the way threw, like a pipe. The shape of the slot keeps the handle from pulling off or out.