Quick answer
Start with the reference number. Patek Philippe's published Nautilus line covers 3700, 3800, 5711, 5712, 5726, 5740, 5980, 5990, 5811, 7010 and 7118. A Nautilus 6790 does not appear on that list. A seller who uses 6790 as the model number is either mislabeling a 5711-family watch or selling a replica with an invented name. Ask for the reference and serial on the caseback, then check both with Patek.
If the seller sends photos only, six physical checks do most of the work: case thickness, dial grooves, date window, bracelet taper, clasp engraving, and movement finish.
Patek Philippe Nautilus 6790 Fake Movement Quality: How to Judge It
Case thickness and shape
The Nautilus case is thin. A 5711/1A measures 40 mm across and 8.3 mm thick. Most replicas come in at 9.5 mm to 11 mm. Measure with calipers at the caseback edge, not at the crystal. The bezel is a rounded octagon. Real ones have flat polished top surfaces and a satin flank. Fakes grind the bezel corners round or leave the flank polished.
Lugs sit flush against the case. On a replica the lug seam shows as a step or a gap.
patek philippe nautilus 6790 replica for sale
Dial
The dial has horizontal embossed grooves and a soft gradient, dark at the edges. Check three points.
- Groove depth. Real grooves are cut into the metal plate and hold shadow. Printed grooves look flat under a 10x loupe.
- Date aperture. On the 5711 the window has no frame and sits at 3 o'clock. Edges are crisp. The date font is thin and tall.
- Printed text. PATEK PHILIPPE and GENEVE are sharp. Fakes show ink spread and uneven letter spacing.
Hands and markers
Hands are white gold with polished bevels and a flat top. Luminous fill sits level with the metal edge. On fakes the fill overflows or sits low. Applied hour markers have a polished frame and a flat top surface.
Bracelet and clasp
Links taper from the case to the clasp. Each link has a brushed top and polished bevel edges. Run a fingernail along the seam between two links: real edges are sharp, replica edges feel rolled. The folding clasp carries a deeply struck Patek cross and PATEK PHILIPPE text. Laser etching is shallow and gray.
Movement and caseback
A 5711 built after 2019 runs the calibre 26-330 S C. Earlier examples run the 324 S C. Both are automatic with a 21k gold rotor and Geneva stripes. Fakes use a Miyota 9015 or an ETA clone with a printed rotor and a false jewel count. Look at the balance wheel: the real movement beats at 28,800 vph and the rotor spins with a heavier sound. Caseback engraving is deep on the real watch. Fakes engrave light and the font is wrong on the PHILIPPE letters.
Patek uses its own Patek Philippe Seal, not the Geneva Seal, on watches made after 2009.
Price, papers, and seller
A steel 5711/1A trades above retail on the secondary market. A listing at a fraction of market price with 6790 in the title is not a bargain. Ask for the original certificate, the box, and a service record. Call Patek Philippe in Geneva or an authorized dealer and read the serial. Extraction is the only check that settles the question.