This charming design of a scientific curiosity, the 'Rattleback', is by Dr Vladimir Krasnoukhov. It features two wooden turtles sitting on either end of a little boat (surfboard?) It is decorated in the manner of a traditional Russian folk toy.
There are two basic types of rattleback. One features a symmetrical hull with off-set weighting at either end; the other has a non-symmetrical hull with a skewed alignment to the keel but no unbalanced weighting. This model belongs to the first category.
The off-set weighting is achieved by swivelling the two turtles so that they face outwards over the sides of the boat but in opposite directions. Spin the toy in the direction the two creatures are facing and it will revolve normally for a while. As it slows it takes up a curious rocking motion from side to side. On certain types of hard surface it may even begin a slow turn in the opposite direction before running out of energy.
Spin it in the opposite direction and the turtles show their dislike of travelling backwards! They seem to jump up and down causing the craft to rattle and rock violently at each end, and then it magically starts spinning the other way!
There are numerous articles on this odd behaviour, including a mathematical analysis by Professor Herman Bondi published in 1986. Rattlebacks appear to have been discovered in the last century. They were originally called CELTS because their odd motion was discovered by archaeologists studying prehistoric axes and adzes, called Celts, that were discovered also to show this strange motion.