There are three basic methods that nutcrackers usually use to open up the nutshell. These are: percussion (otherwise known as hitting it...), with use of a lever, or with use of a screw. Our mystery example obviously uses the last of these methods.
According to The Nutcracker Museum, as long ago the third century, people have been using lever-type nutcrackers to make cracking these nuts easier on themselves. The earliest were as simple as two pieces of wood attached with a hinge. There are many different versions of the lever type nutcrackers, including this common version, resembling a pair of pliers.
This style is very unlikely to be able to crack nuts anymore, however. They are almost exclusively decorative, and this article explains why they have become that way. We mainly think of these kinds of wooden nutcrackers as being the ornate and fancy ones, but it seems like every type of nutcracker has been subject to some fanciful designs, such as these ones: