Most watches feature a bezel that is differentiated visually from the body of the case. Watches without a distinct ring around the crystal can be called "bezel-less" or "integrated", but most have some visible element around the crystal or outside the dial. The bezel can be an important cosmetic element, as is the case with the famous "hobnail" bezel on the Patek Philippe Calatrava, fluted bezel on the Rolex President, and diving ring on the Blancpain Fifty Fathoms.
The term is synonymous with the French "Chaton", which is used in English only when discussing a metal ring around a jewel. The space between the dial and bezel can be occupied by a rehaut, and this is sometimes considered to be an "inner bezel" if it is visible inside the crystal. Some rotating bezels are inside the crystal as well, as is the famous slide rule bezel of the Breitling Navitimer.
The first watch bezels were purely functional and served as a mounting point to attach the crystal to the case. Many of these included the crystal and screwed on to the case similar to today's display caseback. This is the origin of the famous Rolex fluted bezel, a signature of the company today, which could be removed using the same tool as their fluted case back. Another important functional bezel was the rotating bezel on the Harwood, which could be turned to wind the watch.
Early functional bezels include the hour angle used for navigating, a simple rotating pointer for aviation timing, and a rotating 12-hour bezel used to show a second time zone. All of these were in production by World War II, but were not widely seen.
During this same time, the bezel became a decorative element as well. In a 1935 Heuer catalog, four bevel types are listed: Beveled, Curved (concave), Stepped, Coin (or coin-edge). The famous Cartier Santos was one of the first to feature a screwed-on bezel with exposed screw heads. This would become a signature of later sports watches, notably the famed Audemars Piguet Royal Oak, introduced in 1972.
The next major development in bezels came after the war. Rotating bezels printed with hours or minutes became much more common in tool watches, beginning with the Rolex Turn-o-Graph. Dive watches became popular, which use a bezel with minute markers, designed to be rotated to measure dive time. Blancpain invented a uni-directional bezel which turns counterclockwise so dive time can not easily be increased accidentally. Bi-directional rotating bezels are also useful in field watches for solar navigation. Other sports watches are equipped with a bezel with a tachymeter, telemeter, or slide rule.
Designers point out that the bezel defines the "aperture" of the watch, which is the ratio of the dial diameter to the case diameter. Generally, the wider the aperture the "dressier" a watch will appear.
Some bezels feature raised portions known as rider tabs that mark important units, assist in rotation, protect the crystal, or serve decorative purposes. This is a signature of modern Breitling models like the Chronomat as introduced by Ernest Schneider in the 1980s. These original tabs were attached with screws and were removable, and most Breitling models continue to use them.
In the 1980s and 1990s, many watch brands adapted their own fixed tabs, copying Breitling. These became pure styling features, with many included on non-rotating decorative bezels. The popularity of two-tone watches also spread to these tabs on many models.