Case Diameter refers to the measurement across the watch case, typically excluding the crown, indicating the size of the watch face.
There's no universal ideal, but 38-42mm suits most men's wrists well. Classic dress watches typically measure 36-40mm for elegance. Sports and tool watches often range 40-44mm. Proportionality matters most—consider your wrist circumference: 6" wrists suit 38-40mm; 7"+ wrists can wear 42mm+. Personal preference always overrides trends.
Case diameter measures the width of the case at its widest point, typically excluding the crown. It's measured in millimeters horizontally across the case, not including lugs. The lug-to-lug measurement (top to bottom lug tip) is equally important for wrist fit, often more telling of how a watch actually wears.
Yes, dramatically. Vintage watches from the 1950s-70s typically measured 34-38mm. The 1990s-2000s trend pushed sizes to 44-48mm. Today, the market has shifted back toward 38-42mm as collectors rediscover the elegance of historically proportioned watches. Major brands including Grand Seiko and Tudor have introduced more size-appropriate models.