It looks as if its a Simat. Headstock and tailstock tapers are Modified
IIRC the thread is 14x1.5 and Unimat chucks should fit. If the
picture shows all
the bits that are being supplied it's missing the
drive from the spindle to the
lead screw. The back end of the headstock
spindle has a worm drive machined
onto it which meshes with a bronze
gearwheel that is on the end of a shaft with
another worm drive machined
on it which drives another bronze gearwheel on the
end of the leadscrew.
The part that looks like a clock key is the bearing for
intermediate shaft and swings to take the drive in and out of gear.
Should you acquire one I can let you have a copy of the manual.