Found a couple of things when I searched for Powr Kraft vise, not vice. One was this thread:
http://www.garagejournal.com/forum/showthread.php?t=127956 and the other was the picture below. I'm thinking that Milwaukee may have OEM produced the vise for Monkey Wards, but I'm betting that mine is a Powr Kraft. Mine has the identical "screws" holding the jaw pads in. There was a post the other day that someone had of some screwdrivers with funny heads and they were identified as some sort of clutch bolt or screw. The Milwaukee vises seem to have Phillips head screws from what I've seen. Mine, however, does not have "Made in USA" stamped on it anywhere, so it could be a 60s or even 70s Japan vise, but I would expect Japan or the COO to be on it somewhere. Mine has jaws of just under 4".
I'm in the process of electrolytically de rusting the vise and taking off the red paint from the orginal green. Its cleaning up pretty nicely and I'll post some pictures once I get it done and back together.