If that's what it is, it's called a slugging or striking wrench. Very common where there is no power available. A little hard to control torque I reckon, but a practical solution to a problem. I think Armstrong and Proto still make them, don't know who else.
How about this question: I also took possession of a couple large drawers of drills and taps. Most of the taps have a nut tack welded onto the end. Is this just for ease of tapping or is there some other purpose?
Mike, most if not all of the slugging wrenches I've seen are longer and have a greater mass on the striking end. I think I have seen them in the SnapOn and Matco catalogs now that you mention it.
Like Greg, making up flanges is where i have used them. Hard to beat if you want something tight. Or if you need to break it free.