The Casio AD-521 is a rare vintage analog-digital diver's watch from Japan, featuring a black bezel, stainless steel case, and a water resistance of 100 meters. This watch has a unique left-handed design with a screwback caseback and a bidirectional rotating bezel. The watch comes with five spare movements, making it a great option for watch enthusiasts and collectors. With a nylon NATO strap, black dial, and a case size of 43mm, this watch is perfect for those who appreciate a blend of style and functionality in their timepiece.