The short answer
Rolex has never made a Submariner with the reference 126617LB. The current 41mm Submariner Date line covers 126610LN, 126610LV, 126613LN, 126613LB, 126618LN, 126618LB and 126619LB. In practice, sellers who list a "126617LB" mean the two-tone steel and yellow gold Submariner Date with the blue dial, reference 126613LB, which collectors call the Bluesy. Treat the number as a listing quirk, not a spec sheet.
What the watch behind the number actually is
The Bluesy is a 41mm Oyster case in Oystersteel, paired with an 18k yellow gold bezel, winding crown and center bracelet links. The dial is blue with a sunray finish. The bezel insert is blue Cerachrom ceramic, and the numerals on it are coated in yellow gold. Inside sits the caliber 3235, a 28,800 vph movement with a 70-hour power reserve and a Chronergy escapement. Water resistance is rated to 300 meters.
That combination is what a replica has to fake: two metals, two finishes, and a gold tone that has to sit next to steel without looking cheap.
What separates a solid build from a bad one
Gold and steel
Genuine two-tone Rolex uses solid 18k gold for the bezel, crown and center links. Replicas use plating or gold wrapping over steel. Thicker wrapping, roughly 5 to 10 microns, holds color longer. Thin plating fades at the clasp and crown first, and it tends to look brassy or orange next to real yellow gold. Look at the sides of the center links, not just the top.
Movement
The tiers break down fast here. Budget builds run an unbranded 2813 or similar, which feels rough when you set the time and often has a stuttering sweep. Mid-tier builds use an ETA clone like the 2824 or 2836. The closest thing to the real caliber are the clone 3235 movements, sometimes labeled VS or VR. They beat at the right rate, keep the crown position stack correct, and take a decent regulation. Ask for a timegrapher photo or video.
Bezel insert and dial
On the genuine watch the ceramic insert is a deep, even blue and the numerals are gold-filled by PVD. Replicas get the blue wrong in both directions: too bright, too purple, or matte where the real one has depth. Painted numerals flake and look flat. The dial matters just as much. The sunray finish should shift from light blue in direct light to near-navy in shade. Flat spray-painted dials do not move.
Crystal, cyclops and date
Rolex puts an anti-reflective coating on the underside of the crystal, and the cyclops magnifies about 2.5x. On cheap replicas the cyclops looks like a bubble sitting on the glass, the date font runs too bold, or the wheel sits off-center. On better builds the date is centered and the dark ring around it is subtler.
Case and bracelet fit
Look at where the end links meet the case. On a good build the solid end links sit flush with no step and no rattle. Crown guards should be symmetrical and slightly rounded, not slab-sided. The rehaut engraving around the dial should line up with the crown at 12.
Weight
A genuine two-tone Submariner Date on a full bracelet lands around 160 grams. Replicas come in light, often 130 to 145 grams, because of the plated links and the movement. Weight proves nothing on its own, but a watch that feels hollow on the wrist is usually hollow in the case too.
Checks I would run on QC photos
- Gold tone shot in daylight and in shade, not only studio light
- Date centered at the 3 o'clock window, font weight compared to a reference photo
- Cyclops magnification and whether it distorts at an angle
- Bezel insert color next to a known-good photo
- End link fit at all four lugs
- Clasp code, crown engraving and the safety catch action
- Timegrapher reading: rate, amplitude, beat error
- Caseback threads and gasket condition if you plan to wear it near water
Water, service and long-term care
Assume nothing about water resistance until a watchmaker pressure tests it. Plated gold wears at the clasp and crown over months of daily wear, and there is no fix short of re-plating or replacing the part. Clone movements can be serviced, but parts are hit and miss, so many owners budget for a movement swap instead. Rinse the bracelet with fresh water after heavy sweat, and keep it away from chlorine and salt.
Legal and practical reality
In the United States, trafficking in counterfeit goods is a federal offense under 18 U.S.C. § 2320, and Customs can seize shipments. That does not stop the market, but it does shape how sellers ship and what recourse you have if a package is stopped. Read what a seller promises about replacements and returns before you send money.
Bottom line
If a listing says 126617LB, you are looking at a two-tone blue Submariner Date replica, whatever the seller calls it. The number itself tells you the listing was not written by someone with the catalog in front of them. Judge the watch on gold thickness, movement, insert color and case fit, and ask for photos of the actual piece before you pay.