Robert Houdin Square Dial Mystery Clock. Paris, ca. 1850. A “Series 5” mystery clock with a clear square glass dial supported by a decorated brass bezel and topped by a crown. The dial decorated with Roman numerals and cartouches and Arabic numerals at five-minute increments with minute bits between. Four sheets of glass incorporated into the dial – unbeknownst to viewers – are activated by the clockworks in the base of the timepiece to move the hands and keep time. 15 ½ x 6 ¾”. With key. Detailed condition report available on request. Third party shipping required.