These incredible mechanical Works of Art are still working as efficiently today as when they were first made some 250 - 300 years ago.  It is difficult to imagine what mechanical items produced today will still be admired and used in 300 years time.  It is truly remarkable the number of different parts that make up both the movement and the jewel like cases, all of which would have been very expensive to have made at the time and would have been highly treasured pieces.