A replica Patek Philippe 3700 is a copy of the original Nautilus Jumbo from 1976, and the blunt answer is this: it lives or dies on the case. The real 3700/1A measures about 42mm across and only around 7.6mm thick. Push past 9mm and the watch stops reading as a 3700 and starts reading as a generic steel sports watch. Most copies fail there, long before you get to the dial. If a seller cannot tell you the measured thickness with calipers, that is your first warning.
What the reference actually is
Patek Philippe introduced the Nautilus in 1976, with Gérald Genta behind the design and a steel case that borrowed its shape from a ship's porthole. The 3700/1A was the first and the largest of the line, which is where the nickname Jumbo comes from. At a time when a dress watch was 34mm, a 42mm steel Patek was a statement.
Inside sat the calibre 28-255 C, built on the Jaeger-LeCoultre 920 base, the same thin ébauche that powered the Audemars Piguet Royal Oak 5402 and the Vacheron Constantin 222. That shared platform is the reason the 3700 could be so slim. It also means the genuine watch has no seconds hand, just hours, minutes and a date at 3. Remember that detail. It matters later.
Why the 3700 is hard to copy well
Four things separate a convincing replica from a costume piece, and three of them are structural.
- Case height. The genuine 7.6mm profile comes from the movement and the monobloc case working together. A 10mm copy with a fat movement can be slimmed on the outside only so far before the bezel looks wrong.
- Monobloc construction. The 3700 has no separate case back. It opens from the front, with a gasket ring sealing a single machined block. Copies almost always use a screw-down or press-fit back, which changes the side profile and the feel in hand.
- Bracelet taper. The original bracelet flows out of the case and narrows steadily toward the clasp. Cheap copies keep a near-constant width and the whole watch looks slab-sided on the wrist.
- Dial grooves. The horizontal ribbing on the blue-black dial is deep enough to catch light at an angle. Flat, shallow grooves look painted on.
What I check first on a replica 3700
- Measure the case with calipers. Anything over 9.5mm is a pass.
- Look for a seconds hand. The 3700 never had one. A sweeping second hand is the single easiest tell, and a lot of Miyota-based copies have exactly that.
- Read the date window. The disc should sit close to the dial color, not glare white against a dark blue surface.
- Run a finger along the bezel edge. Genuine is brushed on top, polished on the flank. A single finish across both is a shortcut.
- Count the bracelet links and check the taper. It should narrow by several millimeters from case to clasp.
- Check the crown. It sits at 3, it is small, and it should screw down. Oversized crowns are a common mistake.
- Turn it over. The engraving on the clasp and the case reference stamps should be crisp, not sandblasted and faint.
Movements you will find inside
Most replica 3700s run one of three things. The Miyota 9015 and 9039 are reliable and thin, and the 9039 drops the seconds hand, which makes it the better choice for this reference. Decorated clones of the ETA 2824 are common but thicker, and they usually bring a seconds hand with them. A few makers offer a decorated hand-wound or micro-rotor copy of the 28-255, and those are the ones worth paying more for if the case is right.
None of them are the JLC 920. That is fine. Just do not pay a 920 premium for a Miyota movement in a nice wrapper.
Price tiers, roughly
Entry copies under a few hundred dollars tend to be too thick, too shiny and fitted with the wrong bracelet. Mid-tier pieces in the low hundreds to around a thousand fix the dimensions and the dial, and that is where most buyers should land. Top-tier builds push higher, and at that point you are paying for case finishing and a better movement, not for magic.
Red flags
- No thickness measurement offered, only photos at flattering angles.
- Seconds hand on a 3700.
- Water resistance claims above 50m on a copy. Treat it as splash resistant no matter what the listing says.
- Sellers implying the watch is genuine or could pass as genuine. Buy it as a replica, wear it as a replica.
Quick answers
Is a replica 3700 worth it?
Yes, if the case is thin and the bracelet tapers. If either is wrong, the money is better spent elsewhere.
What size should it be?
About 42mm wide and under 8mm thick. Anything over 9mm wears like a different watch.
Does the seconds hand matter?
It is the fastest way to spot a copy, because the original has none.