With a diameter of 36 or 40 mm, the Day-Date Oyster case is guaranteed to be water-resistant to 100 meters (330 feet) and is an example of ruggedness and elegance. The middle case is cast from a solid block of 18K gold or 950 platinum. The Rolex watchmaker uses the brand’s special tools to screw replica watches the fine groove bottom cover tightly to seal the case, so only the watchmaker authorized by Rolex can open the case to access the movement. The double-buckle winding crown has a double waterproof system and is firmly screwed to the case. The bezel is available with triangular pits or diamonds. The mirror surface is made of anti-reflective blue crystal, which is not easy to be scratched. At 3 o’clock, there is a small window convex lens to enlarge the calendar for easy reading. The waterproof Oyster case of the Day-Date type gives the best protection to the movement.Whether in 18K yellow gold, 18K white gold or 18K Everose gold, the Day-Date gold alloys are exclusively produced at the Rolex Goldsmiths.Because 24K pure gold is too deformable, it is not suitable for making watch components. To make it harder and more durable, pure gold must be mixed with other metals. 18K gold came into being, this noble alloy composed of 750‰ (thousandths) pure gold, watchmakers regard it as a treasure. By adding different amounts of silver, copper, platinum or palladium, different kinds of 18K gold can be extracted: yellow gold, pink gold or white gold.