This Object ALWAYS Spins Counter-Clockwise, why?

Hey guys,

I've read these forums a ton over the years and found everything I needed merely by searching. But alas, the day has come where I've needed to create an account to help me with a problem.

I have to determine why this object ALWAYS spins counter-clockwise. Whether you spin it clockwise, tap it, push it - it doesn't matter... pretty bizarre.

Here are some picture and appreciate the help:

In Wales, it is called a rebellious celt. To us, it's the rattleback. "It" is a long, thin plastic toy with a base shaped like the hull of a boat. When you spin it one way, it turns a few times before the ends start to rattle up and down. The more it wobbles, the slower it rotates - until it stops spinning altogether. Finally, it starts to spin in the opposite direction. What could possibly cause this?

The first attempt to analyze rattlebacks was around a century ago. In the mid-1980s, two detailed mathematical analyses were done: one by Hermann Bondi (then Master of Churchill College, Cambridge) and the other by Mont Hubbard (Professor of Mechanical Engineering at the University of California, Davis).

In the mid-1980s, two detailed mathematical analyses were done: one by Hermann Bondi (then Master of Churchill College, Cambridge) and the other by Mont Hubbard (Professor of Mechanical Engineering at the University of California, Davis).