Usually, the thicker a gold case, the stronger it is. The closer the fit of these parts, the better the quality of the watch case. No matter how fine the watch movement, if it is not protected by a good case the watch will not function properly. Water resistant watches have gaskets in the case back and around the crown to keep water from getting into the watch. If removed, the back must be put on by a jeweler to assure water resistance.
Plastic crystals seal themselves.
Gaskets are used to seal glass crystals. The dials of most dress watches are sterling silver or silver coated. Numerals may be printed, embossed or applied. Embossed numerals are raised on the dial. Applied numerals and markers, used in highest quality watches, are 18 karat gold and are mounted separately.