Paul,
It looks like it may be wider, but my first thought was that it would fit a 'Webster Whitcomb' bed **LINK** … which became the de-facto standard for 'modern' Watchmaker's lathes etc.
http://www.lathes.co.uk/derbyshire/
I agree that the chuck looks like it's on the wrong end of the spindle !!
… or rather that the spindle has been inserted wrong way round.
MichaelG.
.
A measurement across the vee would help.
Edit: Just noticed that, on the linked page, captions for the WW and Geneva pattern beds are confused !!
Edited By Michael Gilligan on 26/05/2018 20:07:22