A watch sold as a Blancpain Villeret 6654 tends to fail on one of five points: the serpentine date hand, the calendar correctors set into the case band, the moonphase disc, the finishing visible through the sapphire display back, and whether the serial numbers on the case, certificate, and warranty card agree. Start with the display back. The complete calendar layout on this reference is genuinely difficult to copy, because the date is read by a long curved hand sweeping the numerals printed around the dial edge instead of through a small window, and that single detail trips up most counterfeit attempts.

Check one: the serpentine date hand and calendar layout

The Villeret complete calendar puts day and month in twin apertures below twelve and a moonphase aperture above six, with a blued steel hand pointing at the date around the outer track. That hand has a distinctive S curve, and its tip lands precisely on each numeral.

• Signs that hold up: the hand is heat blued, so it shifts color slightly under different light; printing around the date track is sharp at 10x magnification; apertures are cleanly cut with no burrs.
• Red flags: a painted or anodized blue hand; a straight or clumsily bent hand; the tip stopping short of the track or overshooting it; day and month discs with flat, generic typefaces.

Check two: the moonphase disc

A real moonphase is gear driven from the calendar train and advances roughly once per day, completing a cycle in about 29.5 days. The moon itself is usually rendered with some surface detail rather than a flat circle.

• Signs that hold up: the disc moves a small amount each day; the star field is part of the disc, not a decal; the aperture edges are polished.
• Red flags: a moon that jumps only when the date changes; a sticker or printed insert visible through the aperture; a disc that never seems to advance at all.

Check three: correctors, crown, and case

Blancpain sets the day, date, month, and moonphase with recessed correctors in the case band, using a pegwood or the tool supplied with the watch. This is one of the hardest things to fake because it requires real case machining.

• Signs that hold up: correctors sit flush with the band and press with a firm click; the crown is signed and threads smoothly; the case has a stepped bezel with polished and brushed surfaces that meet cleanly.
• Red flags: no correctors at all; a seller telling you to set the calendar by winding the hands through twenty four hour cycles; shallow or blurry engraving on the caseback.

Check four: the movement under the display back

This is where the decision usually gets made. Open the back, or ask the seller for a clear photo of the movement, and compare the finish with published photographs of the caliber.

• Signs that hold up: Geneva stripes on the bridges, circular graining, blued screws, an engraved balance cock, and a rotor with crisp engraving.
• Red flags: a plastic movement spacer, stamped or laser etched rotor text, uneven striping, no decoration at all on the bridges, or a jewel count that does not match the reference.

Check five: dial, papers, and serial numbers

Applied gold indices, feuille hands, and clean lacquer or opaline finishing belong on the genuine article. Documentation matters just as much.

• Signs that hold up: the caseback serial matches the certificate and the warranty card; the box and booklet match the production era.
• Red flags: photocopied paperwork, mismatched numbers, glued flat indices, doubled or soft printing, hands that are too thick for the dial.

Who should do what

If you are buying secondhand and the price looks impossible, meet the seller at an independent watchmaker and have the caseback opened before money changes hands. If you inherited the watch, do not trust the box or the paperwork on its own, because boxes and cards are copied far more easily than movements. If you are considering a replica instead of a genuine piece, understand what you are buying: trafficking in counterfeit goods is illegal in the United States, and shipments can be seized and destroyed by customs. A counterfeit also cannot be serviced by the manufacturer, and the calendar mechanism on this reference is exactly the kind of complication a local watchmaker may refuse to touch once parts are needed. Pay for an inspection, not for a story.