That tool was used on the old cars that had the small threaded caps over the spindle and bearings. You would thread that tool onto the hub, after you removed the spindle cotter pin and nut, and then rotate the center stud in towards the spindle until it centered on the depression in the center of the spindle shaft. Additional tightening, would pull the hub off of the spindle. Depending on the type of vehicle you were working on, it would have had either an external brake drum or an internal brake drum.
Interesting tool that is rarely seen today.