Check again on the bottom of the steel rail with the notches on it. A date of mfr should be there.
example 8-66. This number represents when the vise was made.
This vice looks to be one of the first decades made in Chicago.
That is about all I can tell you about it.
I saw that the handle was bent, and that takes some doing, to do this.
Most likely using a huge hammer to tighten down on something.
Sand blast it and look for any cracks in the casting. This is important.
There is lots of info out there on the different tool websites about cleaning, painting,,,,etc.
Let us know with your photos as to how it goes,,,,