The Rolex Sea-Dweller reference 16600T is one of the final, most refined iterations of the legendary deep-sea Submariner derivative, the T-suffix variant produced toward the end of the model's twenty-year run from 1988 to 2008. The Z-serial designation places this example in the 2006 production window, giving it the late-run case construction, sapphire crystal, and the long-running Caliber 3135 that powered the reference throughout its lifecycle. The 40mm Oystersteel case is engineered for professional saturation diving with a helium escape valve at nine o'clock, a feature first patented by Rolex in 1967 to permit safe decompression in commercial dive helium environments. The unidirectional rotatable 60-minute bezel carries the original black aluminum insert, a piece of vintage Rolex DNA that ceramic-bezel successors have not replaced in the eyes of many collectors. The black gloss dial features applied hour markers with luminous fills and Mercedes hands. Powered by the in-house Rolex Caliber 3135, a workhorse Superlative Chronometer with approximately 48 hours of power reserve, paramagnetic blue Parachrom hairspring, and the legacy of being one of the most reliable mass-production movements ever made. Water-resistant to 1,220 meters and worn on the Oystersteel Oyster bracelet with Fliplock extension. 2006 production, pre-owned in excellent condition. Affirm financing available at checkout.