If you want to get a good idea of what the modern watchmaking industry regards as a dress watch, you have to look back in time to the classic, thin watches that used to be worn by many. Common features include a small (by modern standards), gold (or gold-toned) watch, with a classical typeface (either Roman numerals or an elegant Arabic script) or baton markers, set against a plain dial background.
The watches common today, with many features on a larger watch face, were not commonplace until the 1990s, long after mechanical watches had become luxury items of self-expression instead of essential items. In the final days of mechanical watchmaking's mass-production era, dress watches, as we now call them, were par for the course.
Typical dress watches are slim enough to slide easily under the cuff of a dress shirt. This means there is a disproportionate preference for hand-wound mechanical movements or quartz modules as they save on space.
Since dress watch dials tend to be very clean and clear, with an emphasis on elegance rather than embellishment, it is perfectly acceptable to do away with a seconds hand altogether and rely on just an hour and a minute hand to tell the time. Reducing the activity of the dial also further favors an affordable and reliable quartz mechanism, as the tell-tale ticking of a quartz-driven seconds hand will no longer be an issue.
The dress watch industry features one of watchmaking's most hotly-contested tussles. Year in, year out, Bulgari and Piaget set record after record for thinness, passing each other time and time again as the leader in their very exclusive field. A wristwatch made by either of these makers or their storied peers carries with it the very highest pedigree of fashion and Haute Horlogerie, combined in a stylish and skillfully wrought masterpiece.
Dress watches tend to come on leather straps. Some dress watches come on bracelets, which are often "Milanese weave", fine mesh, or "beads of rice" instead of the heavier, solid-link bracelets you would expect to find on a sports or dive watch like a Rolex Submariner, a TAG Heuer Carrera, or an Omega Seamaster.
Because the go-to choice of band is a leather strap, dress watches are most often fitted with ardillon buckles (otherwise known as pin and tang buckles). These look like miniature belt buckles and are quite simple to make. Good quality ardillon buckles will be signed with the maker's logo or wordmark and nicely finished with sharp, definite edges. The one drawback of this style of buckle is that it is quite wear-intensive on leather straps, leading some brands or customers to sub it out for a fold-over clasp.
Dress watches tend to be made in precious metals. 18 karat yellow, white, and rose gold are all common (with rose gold favored over yellow in the modern market). Platinum, tantalum, and other less common materials have also made their way into the dress watch sphere, but these are more rare.
Traditionally, smaller diameters are preferred. In the past, 32-36mm was normal, whereas modern dress watches tend to be in the 38-42mm range. In either case, they remain significantly smaller than their sports watch peers, which tend to measure in at 43mm+.
Popular luxury brands well known for producing dress watches Piaget, Bulgari, Patek Philippe, A. Lange & Söhne, Jaeger-LeCoultre, and Vacheron Constantin. Popular entry-level brands known for their dress watches Rotary, Sekonda, Tissot, Hamilton, and NOMOS Glashütte.