Engineer SOS - Restoration of old Tenoner: How does this mechanism work?

Sorry this isn't a Solidworks question but I know you guys will be able to answer it.

We've just 'upgraded' our tenoner and got an old Wadkin EKA.

It's a great bit of kit but unfortunately it's been a bit abused.  The bolt to secure the screw which locks the heads together is broken and I have no idea how it should function.  The end piece has snapped off and is missing.

Here is a snip from the manual describing it's use.

I think I've identified the Part No. but I don't think spare's are available so we'll have to get one made.  I'm not really sure how it should look.

A clue may be in the Part Description (If I have identified the correct part)  SCREW FOR VEE STRIP

Here's some photographs of what I have.

Here is the Screw wound out to show the recess in the shaft.

It's a little bit worse for wear and looks like someone has been tightening down on the edge.

Here's the broken bolt.  There is evidence of a secondary thread just before the break.

When the screw is wound down,,, (looks like we missing a shim/washer) as here it is a bit low

The idea is that the two heads get locked together so adjustments can be made to both heads at the same time.

It's pretty inconvenient to be missing.

Any ideas anyone how this device works?  We are not locking rotation but vertical travel.

Thanks

SolidworksGeneral