Turner's Cube is a cube...cubed. It's 1.57"-cubed volume contains a smaller cube nested inside, and then an even smaller cube nested inside that. In addition to a creating some neat desktop optics, the Turner's Cube also represents a clever display of technique. The 3 cubes were all machined from a single, solid, 200-gram aluminum cube.
The design stems from an exercise novice machinists used to have to perform to demonstrate their knowledge and skill in calculation, system setup, and precision. Today the machines probably do all the Turner Cube machining themselves, but the result is still pleasing enough to make a decent piece for art and physics lovers, or gift for your Dad to stare at at work.
All 3 Turner's Cubes move around freely in all directions, but contrary to what I originally thought when I saw them, you can't pull the smaller ones out from the bigger ones. Unless you choose to accept my Feat of Strength Challenge.