The Hanayama Cast DISK puzzle is unique in that there are two inter-connected disks with keyed holes that allow them to rotate within each other but only in certain positions. It was designed by renown puzzle artist, Oskar van Deventer.
By a series of proper rotation moves, the disks will separate, although you don’t get a sense of progress as your go through the moves. When reassembled correctly, the two disks slide into each other to form the configuration shown in the photograph here.
Hanayama rates the Cast DISK as a Level 2 difficulty, which I think is about right. It’s a real puzzle in the sense that there are no hidden “tricks” that make the solution easy to repeat.
It’s a little different from most other Hanayama puzzles in that it is made of a lighter-weight metal, possibly an aluminum allow, and is not quite as hefty as most. However, it doesn’t seem to affect the durability or quality, for which the company has become famous.
With some effort, it’s certainly possible to determine the exact set of moves that get you to the solution — turn Disk 1 right two holes, then Disk 2 left one hole, then Disk 1 left one hole, and so on. However, because the puzzle is not so difficult as to need a great deal of time without a studied strategy, it’s more fun to simply fidget with it until the solution comes along.