Need Help! new lathes in but what the heck is this

I got my new lathe in yesterday . Its a 7x14 real bull lathe . Im getting it cleaned up for use but noticed something odd. There is some sort of black thing on the compund rest that iv never seen before . Its not in the manual nor any pics iv seen online of this lathe . I have no idea what its for . Does anyone know? Pics below







It has a set screw,hole and 3 notches in it . Im guessing for some kind of post or something but have no clue



Also while im making a thread i was wondering if someone can help with this. On the crossslide and compound dials theres a lot of back and forth play . I can turn the dial back a 1/4 turn without it moving the compound . WHen i turn it clockwise theres no play.Only when turning counter clockwise. How do i adjust that ? Thanks