I loved the look of this one - you have probably realised by now that I am attracted to shiny things! It is made from a 61mm square grid of chromed metal with grooves cut in the top and bottom surfaces. Attached to it is a shiny brassy ring (25mm diameter) which, on closer inspection is made of two rings held together by magnets. It is not as heavy as it looks but is still really quite robust. The initial aim for this is to remove the rings from the grid and then reassemble them back at the beginning. This is the only Hanayama puzzle I am aware of with other aims - at the 4 inner intersections of the grid are small marks (• to ••••) and these mark additional places where you should try to place the ring. They are in increasing difficulty and I think that it is these that give the puzzle it's level of 9 (or 5).
The initial disassembly took me a out 20 minutes and proved a little frustrating as I had no real way to recall he path I had taken (I ended up removing the first half ring quickly and the second I struggled with and placed it in the starting place for the first without understanding how). The pathways are different before converging on a common stretch toward the exit. Putting it back together was even more of a challenge as I ended up at one point with both half rings in the same orientation (but I think I took different paths!!) After some swearing and starting again I finally managed to complete it and certainly had a feeling of having achieved something.
I have repeated the process 7 or 8 times now and it has felt new each time - maybe it is just me, but I cannot remember the path at all! This means it is always a challenge but is frustrating that there seems to be no real strategy that you can use - I just seem to get there by wandering around the maze. I have managed to complete the first 2 of the secondary challenges and these are definitely considerably harder but again they suffer from the problem that you can only succeed by doggedly wandering around the maze trying to home in on the position. They are made more complex by having to plan the order to prevent the rings obstructing each others progress. Having done the first 2 accessory challenges I'm afraid I got bored and have put it away for now (I may come back to it at a later date). I have given this to several friends (mostly newbie puzzlers) and they have all failed to take it apart - they have given up after 10-15 minutes due to boredom!!
I had wondered whether there was a systematic way to analyse and solve this type of puzzle. After a little discussion with George Bell, it turns out that he has produced an article describing a really detailed analysis of the Cast Duet as well as the Cast Disk. It is quite fascinating and allows you to quickly move the rings to anywhere you want on the plate. If you would like a copy of this document then I can send it to you (contact me here).
I personally enjoyed the initial challenge but feel this is really only for the more dedicated puzzler.