The replica Fifty Fathoms Full Moon is a copy of the Blancpain Fifty Fathoms Bathyscaphe Quantième Complet Phases de Lune, a 43 mm dive watch that pairs a complete calendar with a moon phase at 6 o'clock. Replicas of this model fall into three tiers: budget automatics near $150, mid-tier builds near $300, and top-tier builds near $500 to $700. The moon disc, the calendar windows, and the movement underneath decide which tier you are looking at.
What does "Fifty Fathoms Full Moon" actually mean?
Blancpain does not sell a watch named "Full Moon." The phrase is buyer shorthand that merges the Fifty Fathoms diver line with the full moon phase complication. When a listing uses this wording, it almost always points to the Bathyscaphe Quantième Complet Phases de Lune, reference 5054. Some sellers also apply the term to the Villeret Quantième Phases de Lune, a dress watch with a very different case.
Which reference do the replicas copy?
The genuine reference carries a 43 mm case in steel or black ceramic, a sapphire domed crystal, and the in-house 6654.P automatic caliber with a 40-hour power reserve. The dial layout is the giveaway: day and month in twin apertures at 12 o'clock, a moon phase disc at 6 o'clock, and a serpentine date pointer that sweeps the outer ring. Water resistance is rated to 300 m on the original, a number no replica earns through testing.
Movement tiers inside replica moon phase Fifty Fathoms
- Budget tier: a Seagull or A2824 automatic with a decorative moon disc that moves with the 24-hour wheel. Day and month windows often turn as simple date wheels with no real calendar logic.
- Mid tier: a modified A2824 or Miyota 9015 with a working 24-hour moon disc, independent day and month wheels, and a date pointer that tracks the outer ring.
- Top tier: a clone 6654 style automatic with the four-corner calendar arrangement and a moon disc that advances once per day. Factory names such as ZF and MK appear most often in reseller listings at this level.
Pre-purchase checklist
- Set the watch forward two days and watch the moon disc. It should move one step per 24 hours, not spin with the hour hand.
- Inspect the moon aperture at 6 o'clock. The original uses a curved cutout; cheap copies use a plain round hole with printed stars that sit flat.
- Check the twin windows at 12 o'clock for font weight, depth, and clean edges on the day and month discs.
- Measure the case thickness. Extra calendar modules often add 1 to 2 mm, which pushes the watch off the wrist.
- Confirm the bezel insert alignment and the lume pip at 12 o'clock. Misalignment is common below the mid tier.
- Ask for a movement photo. A clear rotor engraving and perlage finish separate the top tier from the rest.
Does the moon phase work on replicas?
On top-tier replicas, yes. The moon disc runs on a 24-hour wheel and shows the moon through a 29.5-day cycle. Even on a genuine watch, that cycle drifts about one day every two years and seven months, so the disc needs a reset with the pusher now and then.
Can a replica Fifty Fathoms Full Moon be worn in water?
Do not dive with one. Gaskets, case threads, and crown seals on replicas are not rated or pressure tested, and the moon phase pushers add two more entry points. Hand washing and rain are the realistic limit.
Price expectations and legal risk
Expect $140 to $220 for budget builds, $280 to $450 for mid tier, and $500 to $750 for top-tier examples with a clone calendar movement. In the United States, buying or importing counterfeit goods violates trademark law and shipments can be seized by customs. Sellers carrying the model are typically overseas storefronts, not authorized dealers.