Quick answer
A fake Patek Philippe World Timer lives or dies on three things: the city ring, the 24-hour disc, and the movement inside. Most replicas get the layout right and the details wrong. City names sit off-center, the day/night split looks muddy, and the case runs a millimeter or two thicker than the genuine 38.5 mm reference because the movement underneath is a standard automatic with a bolt-on module rather than a micro-rotor.
How the real thing works
The world time complication comes from Louis Cottier, who built the mechanism in the 1930s. Patek Philippe put it in a wristwatch in the 1950s and has kept the layout ever since: one city per time zone around the outer ring, a rotating 24-hour disc inside it, and a pusher at 10 o'clock that jumps the city ring forward one zone per press. You set your own city to 12 o'clock, and the hour hand then reads local time while the disc shows the hour in the other 23 cities.
References worth knowing: 5110, 5130, 5230, and the enamel-dial 5231. The 5230 runs caliber 240 HU, a micro-rotor automatic. That fact matters a lot when you start comparing replicas.
The details I check first
City ring
Count the cities. There should be 24. Then read them. Replicas often carry a stale city list, a misspelling, or the wrong city for a given offset. Font matters too. Patek uses a fine serif, and on cheap copies the letters bleed together or sit a hair off the index mark they belong to.
24-hour disc
The disc splits into two tones for day and night, and the boundary should be a crisp line. On good replicas the halves are distinct. On bad ones you get a soft gradient or a seam that wanders.
Dial center
The 5230 has a hand-guilloché center. The 5231 has a cloisonné enamel map. Both are slow, expensive techniques, and both are where replicas cut corners. Stamped guilloché looks flat under raking light. Printed "enamel" has no depth and no gold wire between the color fields.
Movement and case thickness
No replica runs a true 240 HU. Look through the display back for a full-size rotor, or ask the seller what powers it. Most use a modified Japanese or Chinese automatic with a world time module stacked on top, which adds thickness and changes how the watch sits on the wrist.
Hands, markers, crown, pusher
Hour and minute hands should be faceted, not flat stampings. The pusher at 10 o'clock should click firmly and advance exactly one zone. Mushy action, or a jump of two zones, means the module is cheap.
What you get at each price level
- Under about $250: correct layout, wrong everything else. Thick case, flat dial, stamped hands, sloppy city ring printing.
- $300 to $600: decent case finishing, a clean city ring, and a movement that at least looks plausible through the back. This is where most buyers land.
- $600 and up: sharper dial printing, better markers, sometimes a closer case profile. Still not a micro-rotor, so still not the real thing.
Before you buy
Ask for three photos: the city ring shot straight on, the dial at an angle so you can judge whether the guilloché has relief, and the caseback. Then ask which movement is inside and how thick the case measures. A seller who dodges those questions is not worth your money.
One last note. A fake is a fake. Patek Philippe has never licensed a replica, and passing one off as genuine is fraud in most countries. Buy it because you like the look of a world timer, not because you plan to fool anyone.