Quick answer
Most fake Patek Philippe 7118 blue dial watches fail on three checks: case measurement, dial color under raking light, and movement finishing behind the sapphire back. A genuine 7118/1A measures 35.2 mm across the case and roughly 8.6 mm thick, runs a self-winding 324 S C movement, and shows crisp Geneva stripes, polished bevels and a correctly engraved Calatrava cross on the rotor. Copies sit 1 to 2 mm off in one direction, show a flat blue dial with no relief, and hide a decorated stock movement. Measure first, inspect the dial second, open the back third.
Prerequisites
- Digital calipers reading to 0.01 mm
- 10x jeweler's loupe and one bright, diffuse lamp
- Reference photos of the 7118/1A blue dial from a Patek Philippe catalog or an auction house listing
- Digital scale accurate to 0.1 g
- A watchmaker who can open the case back, or a Patek Philippe service quote
Step by step
- Place the watch on a clean surface under diffuse light and measure the case diameter across the 9 o'clock to 3 o'clock line. The genuine figure is 35.2 mm. A reading of 34 mm or 36.5 mm ends the inspection.
- Measure case thickness from the crystal top to the center of the case back. The spec is about 8.6 mm. Copies run thicker, often past 10 mm, because the case has to swallow a stock third-party movement.
- Weigh the full bracelet and record the number. A plated case with hollow links reads light for its size. Weight flags a watch for closer work but never proves anything on its own.
- Tilt the watch so light rakes across the dial at about 30 degrees. A genuine blue dial has a deep, even blue with a fine horizontal embossed pattern; each groove catches light and produces a band of brightness that shifts as you move. Copies show flat painted blue with no relief.
- Study the applied hour markers at 10x. Genuine markers are solid white gold with faceted sides, sharp edges and consistent height above the dial. Fake markers sit unevenly, show rounded edges, or are brass with a thin rhodium flash.
- Inspect the hands. Genuine baton hands carry a clean bevel down the center, mirror-polished flanks and a flush black lume fill. Copies show wide uneven bevels, burrs and lume that sits proud of the hand surface.
- Examine the date window at 3 o'clock. Genuine aperture edges are crisp and chamfered, the date disc matches the dial, the font is thin and the numeral sits centered. Copies usually show a white date wheel, thick numerals or an off-center print.
- Check the case flanks and the Nautilus ears. Genuine cases alternate brushed tops with polished bevels, and the transition line stays hard and straight. Copies look soft, over-polished, or the line wanders along the flank.
- Look at the crown. The genuine crown is stamped with the Calatrava cross and sits flush between the crown guards. Copies use generic crowns, shallow stamping, or a crown that stands proud of the case.
- Turn the watch over and inspect the display back. A genuine 324 S C shows Geneva stripes, perlage, polished bevels and a gold rotor engraved with the Calatrava cross in the correct font. Copies show stamped or printed decoration and a rotor with play.
- Ask a watchmaker to run the watch on a timegrapher. The 324 S C beats at 28,800 vph (4 Hz) with a power reserve near 45 hours. A reading of 21,600 vph confirms a substitute movement.
- Compare the engraved case number with the Certificate of Origin and the service paperwork. Genuine numbers are stamped deep and match across documents. Copies show mismatched numbers, wrong fonts or laser etching.
Common tells on blue dial copies
- Dial blue shifts to purple or grey in daylight
- Embossed pattern too shallow to catch light
- Bracelet taper wrong where it meets the case
- Clasp stamping shallow on the Calatrava cross
- Sapphire back with heavy blue anti-reflective tint
If you already own the watch
Stop wearing it and stop any resale listing. Take the watch to an authorized Patek Philippe retailer or an independent watchmaker and ask for a written assessment with photos of the movement. That document is what a seller, a marketplace or a card issuer needs when you dispute the purchase.