Photos: Wristwatch windup

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.

The most recent issue of WatchTime, a quarterly magazine for watch buffs, cites statistics from the Federation of the Swiss Watch Industry that show exports of complete watches in 2005 hit $9.68 billion, a 12 percent increase over the year before.

This Patek Philippe 5102 G in white gold features a self-winding movement. In addition to the sky chart, it shows the phases and orbit of the moon.

Patek's 5970 R is a manually wound chronograph that also includes what watchmakers call a perpetual calendar--a mechanical system for displaying the day, date, month and year, including leap years.

Swiss watchmaker Girard-Perregaux's Tourbillon with perpetual calendar. The cutaways in the dial and a sapphire-crystal case back allow the wearer to see most of the watch's interior parts at work. Girard-Perregaux is one of only a handful of watchmakers that produces its own movements rather than buying them from a supplier and retrofitting them for specialized functions.

Jacques Lemans celebrates the 250th anniversary of the birth of Wolfgang Amadeus Mozart (1756-1791) with a line of watches in the composer's honor. The watch on the right features a reproduction of one of the few paintings of the Austrian composer and a copy of his signature. These limited-edition watches will be available only in 2006.

From Russia, with time to spare: Soviet cosmonaut Vladimir A. Dzhanibekov is said to have developed the idea for this watch while he was drifting to sleep aboard the Soyuz-7 space station in 1985. Dubbed the Cosmonavigator and produced by Russian watchmaker Rosinex, this watch is designed to allow the cosmonaut/wearer to input the distance between a space-mission orbiter and Earth; the watch then calculates the point on the ground over which the wearer is orbiting. To the right is a display outside the Rosinex store in Moscow.

The Speznaz Biorhythm Watch from Russian watchmaker Rosinex also was created by cosmonaut Vladimir Dzhanibekov. It is designed to indicate the biological condition of 12 human organs, depending on the time of a day. This edition is limited to 300 copies.

From Geneva-based watchmaker Pilo & Co., the Black Diamond. It features a 25-jewel movement, gold-plated case and 298 black diamonds.

Viola, one of Hong Kong's first watchmakers to exhibit at BaselWorld, introduced watches from the company's "Lost in Time" collection. The watch on the left is marketed as a timepiece for the woman who doesn't want to be preoccupied by time. Playing to customers of the opposite temperament is, on the right, a watch whose 10 hands can track the time in three different time zones.

Guess Watches offers its Wild Child watch, which features a denim cuff with 12 teardrop crystals surrounding the face to create a sunburst effect.