Short answer
The Patek Philippe Grand Complications 5204P is a platinum, manual-wind split-seconds chronograph with a perpetual calendar. Replica versions priced from about $150 to $800 copy the 40 mm case, the dial layout and the strap. They do not carry a working split-seconds mechanism, a true perpetual calendar or a platinum case. Each of those three points is testable in minutes.
What the genuine 5204P is
Patek Philippe launched the 5204P in 2012 as the platinum version of reference 5204. It replaced the 5004, built from 1996 to 2011. Case: 950 platinum, about 40 mm wide and 14 mm thick. Movement: caliber CHR 29-535 PS Q, manual wind, 65-hour power reserve, 28,800 vibrations per hour. Functions: split-seconds chronograph with a 30-minute counter, plus a perpetual calendar showing day, date, month, leap year and moon phase. Patek states the moon phase needs correction one day in 122 years. A synodic month averages 29.53059 days, so a 24-hour disc is not a moon phase.
Prices
Replica 5204P watches sell from about $150 to $800. Listings that add sapphire crystal and a decorated movement sit at $400 to $700. Genuine platinum examples trade at auction for $200,000 and above, with box and papers adding to the result.
Movement inside a replica 5204P
Most replicas use a Chinese manual chronograph in the Seagull ST19 family, or a modified automatic chronograph in the Asia 7750 family, with a calendar module on top. The module moves the day, month and leap year windows off the date wheel. It does not know February. Test: set the watch to 28 February and let it run. A perpetual calendar jumps to 1 March in a common year and to 29 February in a leap year. A module-driven replica shows 29, 30 or 31 February. No replica sold at consumer prices contains a true perpetual calendar. Real perpetual calendar mechanisms need no correction until 1 March 2100, when the Gregorian calendar skips the leap day.
Split-seconds: the function to test
The genuine 5204P stops one chronograph hand while the other keeps running, then the stopped hand catches up. Few replicas do this. Two common versions: the second hand is fixed to the main hand, or it stops but never catches up. Test it. Start the chronograph. Press the split pusher. Watch the two hands. Release the pusher and watch the stopped hand fly back to the running hand. If nothing moves, the rattrapante is decoration.
Case, weight and materials
Platinum has a density near 21.45 g/cm3. Steel sits near 7.9 g/cm3. A steel case of the same dimensions weighs about one third of a platinum one. Many replicas use 316L steel. Some use tungsten alloy, density 19.25 g/cm3, to add heft. Weight alone proves nothing, because a tungsten replica can weigh more than the original.
Checks before buying
- Handle the watch. A 40 mm platinum case feels dense.
- Run the split-seconds test above.
- Advance the calendar across 28 February.
- Watch the moon phase disc for four weeks. A real disc turns about one full circle in 29.5 days.
- Inspect dial printing with a loupe: subdial rings, applied markers, aperture edges.
- Ask which movement is inside and who can service it.
Legal note
In the United States, importing or selling a counterfeit watch violates 19 U.S.C. 1526 and federal trademark law. U.S. Customs and Border Protection can seize shipments.