What the term covers

A fake Patek Philippe perpetual calendar is a watch that copies a reference such as the 3940, 5140, 5320G, 5236P, or 5740/1G. The real versions cost $80,000 to $400,000 at retail or auction. Copies sell for $300 to $1,200.

Perpetual calendar function

A true perpetual calendar shows the date, day, month, moonphase, and leap year. It needs no date correction until 2100. Patek Philippe builds this in house. Ref 5740/1G uses calibre 240 Q. The 5236P uses calibre 31-260 PS QL.

Most copies do not have a true perpetual calendar. They use a base movement, often a Seiko NH35 or a Chinese clone, plus a calendar module. That module tracks 30 and 31 day months. It fails on February 29 in leap years. Some copies show a leap year hand that never moves. That hand is a prop.

Price tiers

  • $300 to $500: steel case, mineral glass, printed subdials, day and date only.
  • $500 to $800: 316L steel, sapphire crystal, gold plating 3 to 5 microns, working month and moonphase.
  • $800 to $1,200: decorated rotor, engraved caseback, correct subdial layout at 3, 6, and 9 o'clock.

Checks on a fake

Look at the leap year aperture. On a real 3940 it sits near the 9 o'clock subdial. On most copies the aperture is missing or painted. Look at the moonphase disc. Real discs have a dark blue background and a gold moon and stars. Copies use a flat printed disc. Check the date font. Patek uses a serif font with thin strokes. Copies use a sans-serif font. Check the caseback engraving. Real engraving is deep and crisp. Copies have shallow laser marks.

Subdial spacing tells more. On the 5140 the three subdials sit at 3, 6, and 9. On many copies the 3 and 9 subdials sit one millimeter too low. That gap comes from the module height.

Legal status

In the US, selling a watch with a Patek Philippe logo and no Patek Philippe authorization violates the Lanham Act. US Customs can seize shipments. In the EU, counterfeit goods fall under Regulation 608/2013. Buyers face no criminal charge for personal use in most US states. Sellers do.

What a buyer gets

A fake perpetual calendar watch tells time and shows a month. It will not track leap years. It will not hold value. Service costs $100 to $250 at an independent shop. Parts are hard to find. Water resistance is untested. Do not swim with it.