To use it you apply pressure to seat the driver into the screw (with a second person guiding it if you need), then push the handles sharply forward. This spins the disc up which then whacks into the end delivering a forward rotary shock. You then grab the disc and pull back which rotates the driver, undoing the screw. You can click it into an alternate runner for doing back up (making sure that it's good and tight).
The book states it's for rusty tank screws and female war workers who may not have built the needed strength for such work. A nice and useful bit of history.
I don't know why they don't still make them.