Is there a real Rolex reference 16666?
No. The Sea-Dweller reference 16666 does not appear in Rolex catalogs or in any known production run. The number is a typing error, and the watch people are searching for is the Sea-Dweller 16660, made roughly from 1978 to 1988 and nicknamed the "Triple Six." A replica of a 16666 is simply a replica of the 16660.
What is the Rolex Sea-Dweller 16660?
The 16660 was the second generation Sea-Dweller and the first to use a sapphire crystal. It raised the depth rating from the 610 m (2,000 ft) of the 1665 "Double Red" to 1,220 m (4,000 ft). It kept the patented gas escape valve on the left case flank that Rolex developed for saturation divers.
Key specifications
- Production: approximately 1978 to 1988
- Case: 40 mm stainless steel, screw-down crown with crown guards
- Case thickness: approximately 15 mm
- Water resistance: 1,220 m / 4,000 ft
- Crystal: flat sapphire, no date magnifier
- Movement: Rolex caliber 3035, 27 jewels, 28,800 vph
- Bezel: 60-minute graduated rotating bezel
- Bracelet: Oyster 93150 with 580 end links
- Lume: tritium, usually on a matte black dial
How does the 16660 differ from the 1665 and 16600?
Against the 1665, the 16660 swaps acrylic for sapphire and roughly doubles the depth rating. Against the 16600 that followed in 1988, the 16660 looks nearly identical but runs the caliber 3035 instead of the caliber 3135. That movement change is the fastest way to separate the two references when the case back is closed.
What matters most on a replica Sea-Dweller 16660?
The case and the helium escape valve separate a convincing replica from a cheap one. The genuine 16660 has a machined valve at 9 o'clock that sits flush with the case flank, while many replicas use a decorative cap that is glued or pressed in. Case thickness matters too, because an over-thick case ruins the silhouette under a cuff.
Checklist before you buy
- Case profile: 40 mm wide, about 15 mm thick, with pronounced but rounded crown guards.
- Helium valve: machined, correctly placed at 9 o'clock, with a visible seam line.
- Crystal: flat sapphire with no cyclops over the date window.
- Dial: matte black, "Sea-Dweller" printed above the depth line, no extra text.
- Bezel: crisp 60-minute graduations and a pearl at 12 o'clock that sits level.
- Case back: engraving that matches the era, including the gas escape valve patent line.
- Bracelet: Oyster-style links with matching brushing and a period-correct clasp.
- Movement: an ETA 2824 clone, Seagull ST2130, or Asian 3135 copy beats at 28,800 vph like the original caliber 3035.
Should you expect a replica to be dive-ready?
No. Replica cases rarely carry a tested water resistance rating, even when the gaskets look correct. Have any watch pressure tested by a watchmaker before it touches water, and treat the helium escape valve as decoration until it has been verified.
Frequently asked questions
Is the Sea-Dweller 16660 the same size as a Submariner?
Both measure 40 mm across, but the Sea-Dweller is noticeably thicker because of the helium valve and the deeper rating.
What movement is inside a Sea-Dweller 16660 replica?
Most replicas use an ETA 2824 clone, a Seagull ST2130, or an Asian-made Rolex 3135-style clone. None matches the finishing of the original caliber 3035, but they run at the same 28,800 vibrations per hour.
Why do people write 16666 instead of 16660?
It is a typo. The reference ends in a zero, and the repeated sixes make the mistake easy to copy from one listing to the next.
Is buying a replica legal?
Rules vary by country, and a replica can never be sold as a genuine Rolex. Many buyers collect them for display, reference study, or daily wear.