S7: those look like the original jaws and yes Rock Island made that version for SEARS/CRAFTSMAN in the late 20's and 30's.
the issues I see are the price cause it's not very big, but more importantly is the holes in the back of the jaw tower and the missing supports on under the jaw which is more of an issue than the hole in the back.
sure for $50 you could probably even use it for a parts vise cause main screw and vise nut are almost worth that much. do you weld? if you do then maybe you can practice by building up the jaw towers and if you have a mill you can really smooth those old welds out.