It's a"table" vice with a bit missing.
It's designed to fit onto a table or thin benchtop and then clamp in place. There should be a threaded rod with a tommy bar coming up through the single threaded hole at the bottom.
You might get away with bolting it in place through the hole if you don't need to move it, but you're very unlikely to find the missing part, unless it happens to match a standard g-cramp which you could adapt.
Or just possibly, it will be a standard Whitworth thread in that hole and you can use a bolt.