Lots going on here, a few simple things first
This handwheel came in a job lot of tools, materials and stuff off Freecycle. It makes traversing the carriage when feeding by hand a lot easier than the original Raglan ball handle
The screwcutting indicator is either from a LittleJohn MKII, or a completely different lathe.
The usual place for the carriage lock is just underneath the cross slide leadscrew. I have moved it to the back to make it easier to reach.