I am lazy, so to play with the S8 Love with fixed tip I just attached the button/cap (instead of using a washer to fix the bearing). Not only that, but I left the little key ring, even though it gives it a slight imbalance. My laziness was rewarded by a nice optical illusion: the ring makes a figure 8 ! Or is it the Stummol8 logo? Well done Maurizio!
It is not due to a strobe effect. In fact, you can see it with constant lighting from the sun or a flashlight. What it requires is directional illumination, you will not see it in diffuse lighting. It is just a geometric reflection effect. Even though it seems you see the ring in two opposite positions, these rings are assembled from reflections of different parts of the real ring while it goes around.
The alignment of the figure 8 depends both on the direction of the lighting and the direction from which you are looking. It the light comes from above the figure 8 will rotate with you, but if it comes from the side it only rotates a small angle.
If you have more than one light shinning from different directions you can get more than one figure 8:
