Similar to an indexed thumb shifter.
1. Black piece on left (between 22 and 23) on the bottom. Scratch appears to be from the 2 ball bearings.
2. Black piece on right (between 18 and 19) on top of #1. Ball bearings in the holes near the edge.
3. Probably the 3 identical pieces stacked on top. The ball bearings go in the notch.
4 Not sure about the cast piece. Hard to say w/o seeing the part attached to the bar. I assume that the part not shown is threaded for the nut and lock washer (may be reverse/left hand thread).
