The Patek Philippe 3700/11 is a Nautilus Jumbo in stainless steel. The "11" is a bracelet code, not a second case. Auction listings show both 3700/1 and 3700/11 for the steel Jumbo, so confirm the exact suffix stamped on the case back. Patek launched the Nautilus in 1976 and built the steel Jumbo until about 1982. The case measures 42 mm across and 7.6 mm thick. The movement is the thin automatic caliber 28-255 C. Replicas fail on three points: case thickness, movement type, and the engraved stamps on the case back. Those three checks settle most questions.
Case thickness and shape
Genuine: 42 mm wide, 7.6 mm thick. Copies run 9 mm to 11 mm. The extra depth comes from a thicker movement and a deeper case back. The case is a monobloc, so the movement enters and leaves through the front once the bezel comes off. Two hinge pieces sit at 3 and 9 o'clock, flush with the band. A side photo at eye level shows the problem faster than any other test.
Movement
Caliber 28-255 C is built on the Jaeger-LeCoultre 920 base. It beats at 21,600 vibrations per hour. Copies use ETA 2824 class, Miyota 9015, or Seiko NH35 movements. Those sit near 4 mm to 5 mm thick, and their bridge shapes differ from the 28-255 C. Ask for a movement photo with the case back open. A closed case back and no photo is an answer in itself.
Case back stamps
A real 3700 has a solid steel back with the reference, a serial number, and the Nautilus name cut into the metal. The letters are sharp and shallow. Serial numbers for the 1976 to 1982 build window fall in the 1.3 million to 1.5 million range. Patek supplies an Extract from the Archives for a fee. That paper lists the reference, the movement number, and the date of sale. A seller who refuses that check is not selling a documented watch.
Dial and hands
The dial has raised horizontal ribs on a black ground. Early 3700 dials read Patek Philippe and Geneve at 12. They do not carry the word Nautilus. The date sits at 3 in a flat frame. On copies the rib edges look soft and the print runs thin or wide. Tilt the watch under a lamp. Real ribbing throws a hard shadow line. Stamped foil does not.
Bracelet and clasp
The bracelet is part of the case, not a bolt-on. It tapers toward a fold-over clasp stamped with the maker's name. Link fit is tight on a real one, with little side play. Copies show gaps at the end links and a clasp that flexes under thumb pressure.
What the fakes get wrong
No replica uses the 28-255 C. That movement does not exist in clone form at 3 mm. Case profile and dial ribbing follow from the same limit. Copy makers rename this reference each year. The case under the name stays the same.
Price check
Steel 3700/1A examples sell in the six-figure USD range at auction. Replica 3700s sell for a few hundred dollars. A seller offering a genuine 3700 for $500 is describing a product that does not exist. Buy a replica as a replica, or buy a real one with papers.
Checks before you pay
- Measure thickness with calipers. Target 7.6 mm.
- Get movement photos. Compare the bridge layout to the 28-255 C.
- Match the serial and reference to an Extract from the Archives.
- Look at the dial ribbing under raking light.
- Have a watchmaker open the case. Patek service centers do not service counterfeits and send them back.