I had a bit of a rummage on the Shapeways marketplace today and came up with some 3D printed gubbins that I'm intrigued by. First up is Stop4Stuff's "Twin Rail Mobius," a set of nested Möbius strips that can be loaded with ball-bearings.
A half shell and 3 rails form a bearing-like structure to encapsulate a train of 6mm balls in a mind-warping cage with a twisting, fascinating movement bringing to life the only pendent of its kind in the world.
Includes a 4mm loop for attaching to a necklace or leather cord.
See the photographs with retro-fitted 31 6mm chrome steel ball bearings... in the bottom photo, the balls have been heated until they 'blue'... check out the video to see how they move by clicking on the little icon below the camera above.