Editorial
The Sea-Dweller 16600 is the last 40mm Sea-Dweller, produced 1989 through 2008, with a 4,000-foot depth rating, a thick sapphire crystal, the helium-escape valve at 9 o'clock, and the caliber 3135. It's the Sea-Dweller a Submariner-loving collector reaches for when they want the saturation-diver pedigree without the 43mm 'Deepsea' silhouette that succeeded it.
Rolex introduced the Sea-Dweller line in 1967 for COMEX commercial divers; the 16600 succeeded the 16660 'triple-six' in 1989 with the caliber 3135 upgrade. Two production generations exist: the early 1989-2000 examples (with tritium dials and rivet-style bracelets) and the 2000-2008 examples (Super-LumiNova dials, solid-link bracelets). The 16600 was replaced in 2008 by the ceramic-bezel 116600 (briefly produced, 2014-2017), and the Sea-Dweller line subsequently moved to 43mm with the 126600.
The 16600 sits as the cleanest 40mm Sea-Dweller for collectors who prefer the Submariner case-size.
Common things to check: dial generation (tritium vs Super-LumiNova affects value and lume-aging character, tritium dials carry small premiums on aged examples); helium-escape valve (the 9 o'clock HEV should sit flush and the gasket should be intact, a leaking HEV is a service item but doesn't ruin the watch); bracelet (the 93160 Oyster with 593B end-links is correct for the era; rivet-style early bracelets are correct on pre-2000 examples); case (over-polishing rounds the case profile, the Sea-Dweller's heft is part of the watch's identity, and worn-flat lugs are a value hit); the rehaut on a 16600 is NOT engraved; engraved-rehaut belongs to the post-2008 116660.
