Rack clock

By request, here is the unusual rack or gravity clock that I have just been working on.  The clock belongs to the class of 'mystery' clocks as there are no springs to wind up or weights to give a driving force so it is not immediately obvious how the clock works.  In fact, the clock is raised on a toothed rack to the top of the case and over the course of the week descends to the bottom.  The source of power is gravity as the name suggests, the weight of the mechanism and brass case being sufficient to keep the clock ticking.  The observant among you will notice I still have to make a replacement minute hand!