You know what Mark, looking at this picture again, I don't think the bolt that plastic knob screws into is original either.
My guess is the two pieces attached to the window frames are original, but someone replaced the threaded bolt and the plastic knob. Reason I say that is the bolt is rusted but the two pieces attached to the upper and lower window frames are not. My windows are just a year older than yours and my latches have zero rust on them. How is the other end of that threaded bolt attached?