Short answer
There is no Rolex reference 1666. The string "1666 6" comes from a five digit Submariner or Sea-Dweller reference that lost a digit or gained a space. The numbers people mean are 16610, 16613, 16600, 16660, and 1665. When a listing uses "Rolex 1666 6" as the model name, the seller is copying a typo from a wholesale sheet or avoiding the real reference on purpose. Either way, the listing does not describe the watch in a reliable way.
What the numbers map to
- 16610 Submariner Date, stainless steel, produced from the late 1980s into 2010. This is the reference behind most searches for this string.
- 16613 Submariner Date in steel and yellow gold, same era, common with a blue or champagne dial.
- 16600 Sea-Dweller, stainless steel, no cyclops over the date, helium escape valve on the case side.
- 16660 Sea-Dweller, the earlier version of the 16600, built from the late 1970s to the late 1980s.
- 1665 Sea-Dweller "Double Red", the vintage model with two lines of red text on the dial.
None of these is a 1666. A trailing 6 in a search box is often the leftover of 16660 typed in a hurry.
Before you judge a replica
- The full reference, in writing, from the seller.
- Calipers for case diameter and lug width.
- A 10x loupe for dial text and engraving.
- Photos of the same watch from several angles, including between the lugs.
How to check a replica against the reference it claims
- Get the full reference in writing, not from a photo caption.
- Measure the case diameter with calipers and compare it to the published spec for that reference.
- Read the dial text under a loupe. Line count, font weight, and spelling should match the reference.
- Check the date window and the cyclops. Sea-Dweller references have no cyclops at all.
- Look at the case side. Only Sea-Dweller models carry a helium escape valve.
- Compare the bezel insert markings to the production era of the reference.
- Check the bracelet end links and the clasp code format against the reference period.
- Ask which movement powers the watch and whether the beat rate matches the original spec.
Red flags in the listing
- The reference is written with a space in the middle or a stray digit.
- The same photo set appears on several different references.
- Dial text is called "same as original" with no close up photo.
- Case size is listed as a range, such as 40 to 42 mm.
- No photos of the reference or serial engraving between the lugs.
Legal note
Counterfeit watches infringe Rolex trademarks. Selling one as genuine is fraud, and US Customs and Border Protection seizes counterfeit shipments at the border. Buying a replica for personal wear is a different question from reselling it, but no replica is a genuine Rolex and none should be presented as one.