Photos: Wristwatch windup

Baselworld 2006, held earlier this month in Basel, Switzerland, is one of the biggest trade shows for retailers and wholesalers in the watch and jewelry industry. It also is a point of focus for collectors of mechanical-movement wristwatches, whose manufacture and maintenance almost became lost arts amid the growing popularity of quartz-movement watches.

Mechanical watches, however, have made a remarkable comeback over the past 20 years, and demand for even very expensive pieces, many of which are displayed at Baselworld, is surprisingly strong. (The timing of a quartz movement, whose source of power is a battery, comes from the precise oscillations produced by a quartz crystal placed in an electric field. A mechanical watch uses no battery or electrical circuits. Instead, it is powered by a coiled, wound mainspring and regulated by a system of gears, levers, springs and wheels.)

One of the brands many collectors follow is Patek Philippe, whose watches, along with those made by Rolex, tend to have especially good resale value.

The watch shown here, the 5002 J, is billed as the most complicated watch in regular production at Patek Philippe. It falls in the category of "grand complications"--watches that incorporate complex timing functions, chimes and astronomic indications such as moon phase. It is a big watch, with 55 jewels, a case diameter of 42.8 millimeters and case thickness of 12.61 millimeters. It is designed to run for up to 48 hours between windings.

Look for more watches, including those showing at Baselworld, to post in this gallery in the coming days.