Short answer

The string "fake rolex 1666 6" does not match any documented Rolex reference. Rolex has never cataloged a watch as reference 1666. The number in that search almost certainly stands for one of three Sea-Dweller references: 16660, the 1980s "Triple Six"; 16600, the last classic Sea-Dweller; or 116660, the Deepsea that arrived in 2008. If a replica listing shows "1666" with no further detail, treat the listing as unreliable until the seller names the exact reference and the case size.

Reference numbers that get mixed up with 1666

  • 1665 Sea-Dweller "Double Red," built in the late 1960s and 1970s. Thick case, domed crystal, 610 m depth rating.
  • 16660 Sea-Dweller, sold from about 1978 to 1989. Sapphire crystal, 1220 m rating, helium escape valve at 9 o'clock.
  • 16600 Sea-Dweller, 1989 to 2008. Slimmer case profile, same 1220 m rating, caliber 3135 inside.
  • 116660 Deepsea, 2008 onward. 3900 m rating, Ringlock case system, 44 mm across.

How to tell which watch you are actually looking at

  1. Measure the case across, excluding the crown. A reading near 40 mm points to 16660 or 16600. A reading near 44 mm points to 116660.
  2. Find the helium escape valve on the left flank of the case at 9 o'clock. No valve means the watch is a Submariner, not a Sea-Dweller.
  3. Read the depth rating on the dial. "1220m=4000ft" belongs to 16660 and 16600. "3900m=12800ft" belongs to the Deepsea.
  4. Inspect the crystal. A domed acrylic crystal indicates 1665. Flat sapphire indicates 16660 or a later model.
  5. Turn the watch over. A Sea-Dweller caseback is solid and deeply engraved. A display back on a watch sold as a Sea-Dweller is a warning sign.

What separates a careful replica from a poor one

  • Case profile. The 16660 has a thick mid-case with flat lugs. Replicas that reuse a Submariner case look wrong from the side.
  • Bezel insert. The pip should sit in a recessed triangle and line up with 12 o'clock. Crooked or painted pips are a common flaw.
  • Dial printing. Depth text on a 16660 sits above the 6 o'clock marker in two lines. Font weight should match the brand text.
  • Movement. A clone of the 3135 beats at 28,800 vibrations per hour and sweeps in steps of eight per second. A cheap 21,600 movement looks choppier.
  • Bracelet. End links should sit flush with the lugs with no gap and no rattle at the clasp.

Before you pay

  1. Ask the seller to name the exact reference number, case size, and movement model in writing.
  2. Request photos of the caseback, crown, and clasp under daylight, not studio light.
  3. Confirm the stated depth rating is a spec claim only. No replica should be taken diving.
  4. Check the return window and who pays return shipping.
  5. Compare the quoted price against other sellers stocking the same reference. A large gap signals a lower grade build.

Any seller who answers those five points with real numbers is worth your time. Any seller who keeps saying "1666" is guessing, and so is the watch they are about to ship you.