Traditionally the surfaces of Japanese puzzle boxes are covered with a thin veneer of parquetry (Yosegi-Kaiku) made up of assorted fine woods native to the mountainous area around Hakone, creating intricate patterns and finely detailed geometric shapes. As a result, they are beautiful objects in their own right. The degree of difficulty is determined by varying the number of steps required to open the box. They can range from the very simple--two or three manipulations-- right up to the virtually impossible-- some 1500 steps! Needless to say, the more complicated boxes are usually (but not always) the most expensive.
The fascination with these puzzle boxes seems to be two-fold. One is the fact that they are a work of art in and of themselves and the second is the skill required to not only design and build the box but also the deductive reasoning required to solve the puzzle and gain access to its contents. Giving someone a gift in a puzzle box is doubly rewarding because the container is as much appreciated as the gift that it contains- perhaps a ring or gemstone or some other precious keepsake?
Interestingly, the complex geometric designs that adorn these boxes (Yosegi-Zaiku is the Japanese term for these veneers of parquetry) are instrumental in concealing the seams along which the various pieces of the box slide and/or rotate. This makes it more difficult to decipher the series of manipulations necessary to open the box- functional art! Though the Himitsu-Bako makers do not create the Yosegi-Zaiku, over the past 200 years certain designs have been handed down from master craftsman to apprentice and the quality of the parquetry, which, incidentally, is paper-thin, is in keeping with the box maker's skill. There are five basic parquetry designs (Yosegi-kaiku): Kikkou, Kuroasa, Ichimatsu, Akaasa and Koyosegi, all of which were created more than a century ago.
Alternatively, some boxes may be finished with Zougan art which is a typical Japanese scene (mountains, waves, etc.) elaborately created by placing thin pieces of inlay on the surface of the box. Zougan finish is more expensive than Yosegi. Beyond esthetics and clever joinery, the Himitsu-Baku craftsman also needs a high degree of technical and analytical skill in order to design, organize and implement the unlocking manipulations (much like a computer programmer designing an algorithm).
One of the most famous puzzle box master craftsmen was Yoshio Okiyama who was born in Hakone in 1925. He learned the craft at his father's knee who in turn learned it from his father. By developing new techniques and making ever more complex boxes (including an unbelievable 122-step monster!), over the course of the last 75 years, Mr. Okiyama established himself as the premier puzzle box creator. He passed away in 2003 and his creations now are collector's items and museum pieces. Fortunately, other talented artists such as Akio Kamei and his apprentice, Hiroshi Iwahara, are keeping the tradition alive.
When buying a Japanese puzzle box there are a number of considerations beyond the visual appeal of the box itself. The size of the box is measured in units of 'sun' (pronounced 'soon' in Japanese). 1 sun is equal to approximately 3 centimeters or 1.2 inches. Typically boxes are 3 to 5 suns (or about 3.5 to 6 inches) in length but much larger and very small boxes are available. Bear in mind that back in the day, the wealthy had chests of drawers built with secret opening mechanisms much like puzzle boxes. Also, unconventional shapes are common, more so now than in the past.
Another important aspect to consider when purchasing a puzzle box is the number of moves required to open it. Though 125-move boxes do exist, they are more of a curiosity and not really practical. Ten moves is plenty to challenge most people and provide enough of an "Aha!" moment when solved. Of course, if your intention is not to challenge a solver but to deter prying eyes then 54-66 moves, which was the most common in olden days, should provide an adequate level of protection.