I've seen this model most often in a case with electric and the knee bar (no pedal). Your case has the hole where the knee lever would have gone - normally the wires on those are bad so someone probably re-wired this for the foot pedal. And that could have been done many, many years ago to update to "modern" connections.
Can you take a picture inside the cover? there should be brackets to hold the knee bar.
When you say one side of the case does not lock - is it missing the bracket? There are two styles of brackets, and while the lock side is interchangeable, the other side is not. The other side will have a bent bracket that hooks into the bottom bracket, or it's got a T bracket that slides down and then out to hold that side of the case.