"A system patented by Armand Schwob et Frères on January 24th 1889 and used later by Cartier in particular. Inspired by Jean-Eugène Robert-Houdin's clocks, it uses transparent crystal discs with serrated edges to carry the hands. These wheels are driven by pinions, concealed inside the case frame.
The magician and illusionist Jean-Eugène Robert-Houdin (1805-1871) is considered to be one of the inventors of the mysterious clock whose movement is usually housed in its base." (FHH)