Short answer: Rolex never made a Sea-Dweller 16666
There is no reference 16666 in the Rolex catalog. If you see that number on a listing, a spec sheet, or a search bar, it is almost always a typo for 16600 or 16660, or a seller copying numbers to catch traffic. No genuine Sea-Dweller left Geneva wearing 16666, so any "16666" you buy is either a mislabeled 16600/16660 replica or a made-up model name. Knowing the real references first makes the rest of the buying process much simpler.
Which reference the seller probably means
- 1665 (roughly 1967 to 1978): the original Sea-Dweller, plexi crystal, 610m rating, helium escape valve at 9 o'clock. The "Double Red" dial lives here.
- 16660 (1978 to 1989): the "Triple Six," first Sea-Dweller with a sapphire crystal and a 1220m (4000ft) rating. Calibre 3035 inside. This is the one people mix up with 16666 most often.
- 16600 (1989 to about 2008): the classic 40mm Sea-Dweller, calibre 3135, 1220m, no cyclops over the date. Tritium dials early, SuperLuminova later.
- 116600 and 126600: the 2014 and 2017 revivals, 40mm and 43mm. Different animal, different price.
If a listing says 16666 and shows a 40mm case with a helium valve and no magnifier, you are looking at a 16600 replica. If the description mentions a 3035 movement and an early sapphire crystal, it is aimed at the 16660.
What I check on a replica Sea-Dweller 16600 or 16660
Case and helium valve
The case should measure 40mm across, about 14.8mm thick, with 20mm lugs. The helium escape valve sits at 9 o'clock and should sit close to the case flank, not stick out like a bolt. On nearly every replica the valve is capped and does not function, which matters only if you plan to dive. The caseback is noticeably deeper than a Submariner's, since it clears the thicker midcase.
Dial, hands, and crystal
Look for the missing cyclops. That alone separates a Sea-Dweller from a Submariner. Marker surrounds should be white gold on a 16600 and sit flat, with no glue bleed around the edges. Date wheel font is a common weakness on cheaper builds: the numbers look thin or sit high in the window. The crystal should be flat sapphire on 16600 and 16660, domed plexi only on a 1665.
Bracelet and clasp
The Oyster bracelet should have solid end links that sit flush against the case with no visible gap at the lug. The flip-lock clasp needs a working diver extension and a firm snap. Feel the bracelet for sharp edges on the clasp cover, which is a tell on budget tiers.
Movement
Cheap builds run a DG2813 or A2836 at 21,600 bph. Mid and high tiers use an ETA 2824 clone or a 3135 clone, which runs at 28,800 bph and winds and sets the way the real thing does. Ask which movement is inside before you pay, because it changes both the price and how the watch feels in hand.
Water resistance
Treat any replica as splash resistant at best unless the seller pressure tested it and can show the result. Crown and caseback gaskets on budget watches are often dry from the factory.
Questions to ask before you pay
- Which factory and which movement? Vague answers usually mean a stock photo.
- Can I see QC photos of the exact watch, including the caseback and clasp?
- Is the bezel insert ceramic or aluminum, and does it click cleanly in both directions? It should be unidirectional.
- What is the return policy if the date font or the lume is off?
Bottom line
Ignore the 16666 label and buy against the real reference. Decide whether you want the 16660 look or the 16600 look, pick a movement tier you can afford, and judge the watch on the case, the crystal, the bezel, and the bracelet fit. That is where the money shows.