Slow shutter speed so you can see the movement of the marbles.
The extra screw in the gear is the 'setscrew' to lock the gear onto the shaft. The holein the big geear is one of the 4 original holes I drilled. At first, I drilled them through but then realized this was a dumb idea. The little protrusion in the hole is to keep the marbles from rolling out the back of the hole. All the other holes are blind holes.
The two nuts on the stick are the counterweight, with a nail stuck in go give it the right balance. The big piece of wood sticking to the top right is the support - it holds this part to the frame of the machine.
Varnishing helps the machine last longer. Rapid decreases in humidity can cause the wood to crack, and putting varnish on it also reduces, but doesn't eliminate the amount of expansion and contraction from humidity. Unfortunately, after varnishing, the machine requires re-debugging.