Jean Eugene Robert-Houdin's success with mystery clocks inspired other clock makers. A French clock maker named Andre Romain Guilmet patented several types of mystery clocks in the 1860s and 1870s. His most famous clocks featured ornate figurines holding pendulums that swung for no apparent reason. The secret was that the figurine stood on a circular platform that moved imperceptibly, just enough to keep the pendulum moving accurately [source: British Museum].
Another man from a French clock-making family, Maurice Couet, began making mystery clocks for the famous French jeweler Cartier early in the 20th century. Cartier mystery clocks were lavishly decorated with diamonds and other jewels, and each handmade clock was set into a work of art such as a gong or miniature temple. Each had a gemstone, usually a piece of rock crystal at its center. The secret to these clocks was that the apparently solid crystal had really been expertly cut in half, and two crystal discs with serrated edges inserted. The clock hands, which appeared to float, were really attached to the discs. And the entire clock, which appeared to hang freely within the work of art, was connected to the top by invisible wires. These relatively newfangled clocks became almost instant collector's items: J.P. Morgan, the American financier, bought the first clock Couet made for Cartier. One in the shape of a temple that sold for $3,200 in 1929 sold at auction at Christie's in 1993 for more than $1.5 million [source: Blauer]. Christie's sold another Cartier mystery clock in 2009 for $530,500 [source: Kolesnikov-Jessop].
In the early decades of the 20th century, the German clock company Junghans made many ornate mystery clocks called swingers. These included such figurines as the Roman goddess Diana, the Egyptian queen Cleopatra as well as random renderings like "Onion Boy," "Barmaid," "Bat Boy, "Elephant," "Zebra" and others. You can still find these originals for sale today, as well as more modern reproductions.
The American clock company Ansonia, in Connecticut, also made figurine mystery clocks that became quite popular. Ansonia's "Gloria" clock is often used as an attention-getter in jewelry store windows. Gloria is a winged female figure holding a clock ball in her hand. The hidden clock workings are inside the ball. An Ansonia Gloria clock sold for $5,175 at an auction in 2011 [source: Kovel]. Many of the most famous mystery clocks were individually handcrafted and were made with jewels and precious metals that increased their value.
Keep reading to learn what happened when modern entrepreneurs tackled mystery clocks.