The fast answer
A genuine Blancpain Villeret Quantième Complet moves its moon through a full cycle in about 29.5 days. Almost every fake moves it in 24 hours, because the "moon phase" is really a day/night wheel bolted to the hour hand. Set the watch, note where the moon sits, and check again the next evening. One full lap means it is not a moon phase at all. That single test settles more arguments than any photo comparison.
What the real complication does
Blancpain's Villeret complete calendar puts day and month windows at 12 o'clock, a moon aperture at 6, and a blued serpentine date hand sweeping a ring of numerals around the outer dial. Calibre 6654 is an automatic with a 72 hour power reserve, and its moon disc is driven by a geared train that steps once per day and returns to the same phase in roughly 29 days and 12 hours. Close enough to the true 29.53 day lunar month that the owner corrects it every few years, not every month.
That gear train is the expensive part. It is also the part counterfeiters skip.
The 24 hour giveaway
Cheap fakes reuse a day/night disc: a two tone wheel that rotates every 24 hours, printed with a moon on one side and a sun on the other. It looks convincing for about ten seconds. Watch the aperture across a full day and the moon slides across the arc while the hour hand makes one lap. A real moon phase barely moves in 24 hours, about a twenty ninth of the small arc.
Some mid tier replicas go further and fit a 59 tooth disc driven off the hour wheel, which gives a 29.5 day cycle but runs fast against the actual lunar month. Over months it drifts. You will not catch that in an unboxing video.
Dial and aperture details
- Moon and stars are crisp, with a defined edge between the moon face and its shadow. Fakes print soft, flat, or off center.
- The aperture is a clean arc cut with an even bevel. Crooked or ragged edges show up the moment you go to macro.
- Day and month discs sit flush under their windows and change with a snap at midnight, not a slow creep over an hour.
- The date ring is engraved and filled, not a decal. The serpentine hand is heat blued steel on the genuine, curled to follow the ring.
- Applied numerals sit proud with polished bevels. Printed ones sit flat and look dead under raking light.
Case and correctors
Blancpain hides the calendar correctors under the lugs. You need a small tool to reach them, and you will not find pushers on the flank of the case. Most fakes put recessed pushers on the case band because it is easier and cheaper to build. If you see four pin pushers around the side of a "Villeret," the case is not following the original layout.
Check the crown too. Genuine Villeret crowns carry a sapphire cabochon or the maker's mark, set with clean edges. Replicas tend to glue in a domed stone that sits crooked or too tall. Lug finishing matters as well. On the real watch, the transition from brushed lug tops to polished flanks is a hard line, not a soft blend.
Caseback and movement
A fake moon phase movement will not look like calibre 6654 through the sapphire back. The genuine rotor, bridges, and perlage pattern are specific, and the balance sits where it sits. Put a caseback photo next to a reference photo of a genuine 6654 and compare jeweling and bridge shapes. Replica movements are built on thinner base calibres with a calendar module stacked on top, so the case is deeper than the original dimensions suggest.
What photos cannot tell you
Weight and sound. A gold case feels dense in a way plated brass does not. A well finished automatic rotor is quiet; a cheap one rattles when you tilt the watch. Ask for a short video with the watch running and listen to it. Then ask for two photos of the moon aperture taken 24 hours apart, same time of day. Anyone selling a real moon phase can produce that in a day. Anyone selling a day/night disc will find a reason not to.
Quick checklist
- Does the moon complete a cycle in 24 hours or in about 29.5 days?
- Are the calendar correctors hidden under the lugs?
- Do the day and month windows snap at midnight?
- Is the date hand blued steel with a serpentine bend?
- Do the movement bridges match a known calibre 6654 layout?
- Does case thickness match the genuine spec, or is it bulked up over a module?
Run those six and you will know what you are looking at, whatever the seller wrote in the listing.