That's really nice.
Reminds me of this one I've been curious about, not mine. Does anyone recognize the distinctive meatball, collar, or handle end? Vise is unmarked, 4-1/2" jaw, 48lbs. Very Prentiss-esque, compare to above.
Definitely a vise with some unique features.
The meatball screw head not uncommon, Rock Island, early Reed's and Parker's come to mind and probably a few others. But the taper right after the meatball going into the vise, never seen anything like that.
Also the collar holding the screw, both Desmond Stephens and Parker used this, but neither had the cast in "collar" on top of the collar; that is quite unique. Also you stated this was a 4 1/2", Parkers had 1 screw holding the collar till you got to 6" or greater, and I do not recall what Desmond did, but this has 2 screws for a smaller 4 1/2".
The C jaws, I remember that American Scale and Rock Island had jaws like this, probably a few others. I am sure when it comes to jaws, Kevin could give you exacting details to which MFR's and models had these.
The base has Reed and Parker attributes, and the rest of the vise has features or details from many of the famous MFR's, but still unique to itself.
Very nice vise indeed.