Headstock Controls.
Almost certainly another pre-production picture showing a rev counter with only one scale - productions versions showed revolutions in both forward and reverse in  separate quadrants. 

Chase Screwcutting Accessory - an unusual fitting to find on a lathe already equipped with a full screwcutting gearbox.
In the "Chase" of screwcutting a rear mounted holder carried a "Master Thread" - tucked up underneath the headstock - and a long "transmission bar" on which the cutting-tool slide pivoted and slid. The Master Thread was also variously known as a hob, leader or former was available in various pitches.
A "half-nut", held in the end of an arm connected to the "transmission rod", pressed on the thread and conveyed its pitch, via an adjustable toolholder, to the workpiece. The interconnection of the cutter holder and the half nut allowed the nut to be lifted out of engagement and the cutting tool returned by hand to the start without stopping or reversing the lathe. A little additional depth of cut could then be applied by the tool slide or "stop screw", the half-nut rested back on the Master Thread - and the cut restarted. 
Whilst this system produced was able to produce very accurate and very fine threads - and was especially suited to delicate operations on thin-wall tubes used to construct items as such microscopes - the length of thread that could be cut, and the number of threads per inch or mm, depended upon the availability of the appropriate thread master - although in the case of the Holbrook additional gearing was provided to extend the threading range of each Master Thread by several multiples. 
A very simple form of this screwcutting mechanism, which shows the layout and method of operation very clearly, can be seen on the Goodell-Pratt Pages.