Pre-owned Rolex Submariner 16600. Both the case and bracelet of the 16600 is made of 904L stainless steel. The Sea Dweller was designed for diving professionals that need a timepiece that could go a lot deeper and withstand the harshness of saturation diving. This timepiece features a waterproof rating of 1,220 meters (4,000 ft) which should be more than enough for most professional divers. Deep sea divers use a helium/oxygen mix in their tanks when going for a dive. Helium pressure can penetrate the crystal of the watch and can accumulate pressure due to decompression. Early deep sea divers literally saw the crystals get blown out of their watches. Rolex has addressed this issue by adding a helium escape valve into the Sea Dweller. This mechanism lets out the helium pressure once it reaches a critical point. The addition of the Triplock crown adds another layer of water resistance. Brand: Rolex Model: Sea-Dweller 4000 Reference: 16600 Case: Steel Movement: Automatic Dimension: 40mm Dial: Black Bezel: Steel Crystal: Sapphire Bracelet: Oyster in steel Original box and papers: no Year: 1999 Condition: Very Good