When its working properly the tension provided by the spring would twist the blade clockwise, that would force the block up against the screw thread.
When the QR lever is pushed in the blade flattens out, and the block drops, allowing the jaw to be pulled out as the screw thread isn't in contact with the block any more.
I did get some tension on the spring by spinning the blade through 180 degrees, this sort of worked, until you used the QR, once it was released the blade would fall out of the slot, letting the block drop and thus stopping the whole thing from working at all. I think this happened because there was too much tension on it.
Finally, not much I can do about this, part of the casting is missing, meaning one of the bolts is missing and has nothing to screw in to anyway as it looks like part of the casting chipped out. There is just a single bolt that holds this on in the opposite corner to the one pictured - one bolt is enough to hold it, but its not ideal.
You could fix the missing screw with a blob of epoxy putty and a new screw. But the main problem seems to be the plate on the bottom that positions the release bar---yours is broken. Check the pics of my Record 23.










