you forgot to include the dollar bill (or quarter, or beer can) for scale. Looks like a bushing driver, or something.
Good question. I have a bushing driver set for automatic transmissions, that has several tools similar to that. But yours appears it could be home made (on a lathe) for some specific application. If it has a name and numbers stamped on it, it might be store bought. It's one of those things that I wouldn't waste much time worrying about.
Measure the diameters of the shaft and the narrowed end. compare the narrowed end to the inside diameter of the usual kingpin bushings, and the shaft to the outside diameter of those bushings, and I'll bet you'll find it fits something common.