A simple mechanical watch contains roughly 130 components. More complex watches contain hundreds of parts. The Calibre 89 made by Patek Philippe contains 1728 parts and is probably the most complex watch ever produced.

The main parts of a simple mechanical watch include:

• the mainspring, which provides the power
• the balance wheel and hairspring, which oscillate, thereby marking the division of time
• the escapement, which distributes the impulses from the oscillator
• the gear train, which transmits the power
• the winding stem (in manually wound watches) or the oscillating weight (in self-winding watches)
• the dial train, which activates the hands

The internal mechanism of the watch is called the movement.

Complications

A complex watch displays much more information than simply the time of day. Such extras are known as complications. They may commonly include a display of the day of the week and of the month, and a stop watch facility. Chimes are another kind of complication. If a watch contains all of these, plus astronomic indications, it is called a grand complication.

The complications of the Patek Philippe Calibre 89 include the phases of the moon, the date of Easter, the times of sunrise and sunset, indications of sidereal time and a star chart. The watch was made to mark the 150^th anniversary of the firm in 1989; only four were produced. One was sold at auction in Geneva in 2004 for over 6.6 million Swiss francs.

The most complicated automatic winding wristwatch to be produced as a series (limited to 30 pieces) is the Blancpain 1735, which contains 740 components, each one individually adjusted, hand-finished and hand-decorated. Some components are no thicker than a human hair, and their intricacy is such that very few watchmakers have the skills required to make all of the complications. Each watch takes a year to craft.

Watchmakers over the centuries have striven to expand the range of complications. One of the most famous clocks ever made was the “Marie Antoinette”, commissioned for the French queen in 1783 from the great Swiss-born watchmaker, Abraham-Louis Breguet (1747–1807). It incorporated all the advances of the 18^th century, but it was such a complex commission it was not completed until after Bréguet’s death, many years after the queen herself had gone to the guillotine.

The virtually unsaleable “Marie Antoinette” passed through many hands, before finding a permanent home in the collection of Sir David Salomon, which he had donated to the L.A. Meyer Memorial Institute of Islamic Art in Jerusalem.  However, this home proved to be not so permanent – on the night of April 15-16 1983, the watch was stolen and its whereabouts remained shrouded in mystery for many years.

In 2005, Nicolas Hayek, who by this time was in charge of a watchmaking empire that included Bréguet, decided to commission an exact replica of the “Marie Antoinette”. Over three and a half years, ten watchmakers worked day and night to recreate the legendary timepiece, relying only on the few drawings and photos of Bréguet’s original to help. To much fanfare, Hayek finally unveiled the exquisite replica at Baselworld 2008.