looks like a belaying pin but those slipped into the holder. might be from a cat post. wood might be lignum vitae it is hard as hell and lasts forever.
Got me stumped,looked at rear handles to hay knives,a ferrul would have covered grooves and strengthened area around hole. Of course by then its big enough a handle for a farriers file!.
a farriers file might fit but you would have to have some big hands to hold that thing. I like what WWWtimmcp said about being a Belaying pin because of a few brass objects i have found recently in the same area matching items from a boat.