those look pretty cool when restored and they come in handy if you have one that has all the parts. i don't see any cracks in the cast so i'd say keep and restore. my version of restoring that would be to put in Electrolysis for a few days to get rid of the rust, wire wheel off the excess gunk, then a few coats of BLO (boiled linseed oil). i'm not a fan of paint on old steel.
here's a great "HOW TO" thread on electrolysis if you haven't tried it yet that will also work well on your vise if you keep it.
