Mechanical movement vs Quartz movement
Mechanical movement watches must be wound, or if they are “automatic” they will self wind via a weight that swings with the movement of your body. If you are not attentive to winding and wearing a mechanical watch it will not keep good time. You can buy special watch boxes that revolve, essentially charging the watch for you. Mechanical movement watches never need batteries and are usually more valuable.
Quartz movement relies on a battery to operate. These watches are usually more accurate, and can be left on your dresser for months and months before the battery runs out and the watch stops keeping time. Quartz movement is seen as less sophisticated by watch connoisseurs, but ultimately it is more reliable and less expensive than mechanical movement.
Digital watches
If you really care about your appearance, digital watches are only acceptable to keep time when exercising or when worn by someone under the age of 12. I guess I’ll give residents of the international space station a pass as well.
The watch crystal (ie the watch face)
It is a bit embarrassing, but I was a confused by the term watch crystal before I began to research watches for myself. I always assumed the watch crystal had something to do with “quartz movement.” As it turns out the watch crystal is the hard, clear covering that protects the face of your watch from the elements. There are three types of watch crystal, from cheapest to most expensive: acrylic (plastic), mineral crystal (glass), and sapphire crystal. As you move up the price scale you get increasing durability and ability to withstand scratching.

The bracelet (wrist band)
Leather is always a classic choice, if you cannot afford a brown leather strap and a black leather strap it is permissible to wear the one color you can afford all the time. Often the price of leather or exotic skins (lizard, ostrich) runs the same, or even more, than a metal bracelet. While skins don’t have the durability of a metal bracelet, they are worth the investment for the classic look and the visual interest they add to your wrist. Skins are also less flashy than metal bracelets. I prefer the look of a skin bracelet for day, and a metal bracelet for evening.
Bejeweled watches
Bejeweled watches are best left for formal occasions by men or women past their teens. If worn on a day to day basis a watch adorned with diamonds, or other precious stones, is ostentatious and should therefore be avoided. Similarly, a bejeweled watch worn by a teenager reflects poorly on their over indulgent parent. Perhaps if one works in the rap industry it is permissible to wear diamond encrusted watches during the day time, but really understated sophistication is almost universally admired over blatant display of wealth.

Chronometer vs Chronograph
A chronometer is an extremely accurate watch and a chronograph is a watch outfitted with a stopwatch function. A chronometer is very expensive and must be certified. A chronograph can be purchased quite cheaply. Sometimes more is just more; unless you have some daily need for a stopwatch I would avoid bulky, overly complicated chronographs outside of sporting activities.
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