Short answer
A replica Patek Philippe perpetual calendar copies a specific reference, most often the 5140, 5327, 5236P or the 5740/1G Nautilus. It is not a Patek Philippe. The movement inside is a base calibre from China or Japan with a calendar module added on top. That module is the hard part, and it is where most replicas fail. Check four points before you pay: dial layout, case thickness, corrector function, and the moon phase disc.
What a perpetual calendar does
A true perpetual calendar tracks the 28, 30 and 31 day months and inserts February 29 in leap years. The gear train carries a four-year cam, so the watch runs from March 1 of one year to February 28 of the next without a push. Patek Philippe states that its calibre 240 Q based perpetual calendars need no manual correction until 2100, because 2100 is not a leap year. A complete calendar, by contrast, needs a pusher press at the end of February. Many replica listings use the two terms as if they were the same. They are not.
References that get copied
- 5236P: in-line perpetual calendar, single aperture at 12 o'clock for day, date, month and leap year, moon phase at 6 o'clock, 41.3 mm wide and 11.07 mm thick in platinum, calibre 31-260 PS QL, released 2021.
- 5740/1G: Nautilus perpetual calendar, 40 mm, calibre 240 Q, steel-look bracelet, ultra-thin case.
- 5140 and 5327: classic round cases with three subdials and a micro-rotor movement.
- 3940: the 1985 original that set the subdial layout most replicas imitate.
Pull the reference page from patek.com and compare the dial before you look at any listing photo. Subdial count, hand shape, printing and aperture position are all documented there.
Four checks
1. Moon phase disc
A real moon phase completes one cycle in about 29 days, 12 hours, 44 minutes. Cheap replicas fit a disc that turns once per 24 hours, linked to the day and night wheel. Watch the disc for two nights. If the moon moves a full quarter of the aperture overnight, it is a day and night disc with a moon graphic.
2. Correctors
Genuine perpetual calendars set the day, date, month and moon phase with recessed pushers set into the case band. Press each one with a toothpick and watch the jump. A dead pusher, or one that moves the wrong subdial, means the module is decorative or misassembled.
3. Leap year indicator
The leap year aperture or hand should show a four-year cycle. Replicas sometimes reuse a 24-hour hand and print 1, 2, 3, 4 under it. The hand will then sweep a full turn each day instead of stepping once per year.
4. Case thickness
Calendar modules add height. A copy of the 5236P that measures 14 mm or more is not close to the 11.07 mm original. Ask the seller for a caliper photo of the case back to case front.
Movement reality
Most replica perpetual calendars run a Miyota or Seagull base with a piggyback module. A smaller number use a copied micro-rotor calibre. Service is the practical problem. Parts for the module are not catalogued, and many watchmakers will not touch a counterfeit. Water resistance is not tested by the maker, so treat any rating in a listing as unverified.
Legal position in the US
Goods that carry a registered trademark without authorization are subject to seizure at import by U.S. Customs and Border Protection. Selling them can be charged as trademark counterfeiting under 18 U.S.C. § 2320. A "Swiss made" stamp on a watch assembled outside Switzerland is also a false description. Buyers should know this before ordering from an overseas seller.
Price bands
Listings sit in three rough groups. Under about $300, the calendar functions are partial and the moon phase is a 24-hour disc. From about $300 to $700, the correctors work and the case is closer in profile. Above that, buyers are paying for a copied micro-rotor movement and better dial finishing. No price makes the watch a Patek Philippe.