A paragon of robustness and reliability, the 40 mm Oyster case of the GMT‑Master II is guaranteed waterproof to a depth of 100 metres (330 feet). The middle case of the version presented is crafted from a solid block of 18 ct white gold. The Triplock winding crown, fitted with a triple waterproofness system and protected by an integral crown guard, screws down securely against the case. The crystal, which features a Cyclops lens for easy reading of the date, is made of virtually scratchproof sapphire and benefits from an anti-reflective coating. The waterproof Oyster case provides optimal protection for the movement it houses.