What Is the Replica Fifty Fathoms Full Moon?
The replica Fifty Fathoms Full Moon is a copy of the Blancpain Fifty Fathoms Bathyscaphe Quantième Complet Phases de Lune, a dive watch that pairs a complete calendar with a moon phase window at 6 o'clock. Copies run from about $40 for budget quartz builds to $500 for high-end reproductions, and the moon phase mechanism is what separates those groups.
Blancpain's official model name is long, so sellers shorten it. You will see the same watch listed as a Fifty Fathoms moon phase replica, a Bathyscaphe complete calendar, or a Full Moon. The real watch is a 43 mm steel Bathyscaphe with day, month, date, and a moon disc.
How the Real Watch Works
Blancpain builds this model around the 6654 automatic movement. The dial shows day and month in windows near 12 o'clock, a date indicator, and a moon phase disc that tracks the 29.5-day lunar cycle.
A complete calendar knows month lengths only up to 31 days. The owner resets it at the end of February and after each 30-day month, which works out to five corrections per year. A perpetual calendar handles this on its own. The Blancpain model is a complete calendar, not a perpetual one.
That detail matters for buyers. Replicas rarely copy the 6654 movement at all, and most use a generic automatic or quartz base with calendar modules bolted on.
Replica Tiers and What You Get
The market splits into three rough groups. Price tracks the movement, the case finishing, and the moon phase mechanism.
- Budget (about $40 to $80): quartz or basic automatic, printed dial, a disc that turns once per day instead of once per month, often 42 to 45 mm.
- Mid tier (about $120 to $250): automatic with day, date, and month, mineral or sapphire glass, and a working moon phase on some listings.
- Top tier (about $300 to $500): cloned or modified automatic movement, sapphire crystal with anti-reflective coating, decorated rotor, correct 43 mm case, moon phase geared to 29.5 days.
Prices move with supply and demand, so treat these as ranges rather than fixed numbers. A seller who quotes $600 for the same build another seller lists at $320 is marking up the same watch.
How to Tell a Real Moon Phase From a Fake One
The moon phase is the easiest part to check, because a cheap copy cannot hide a 24-hour disc. On a correct moon phase, the disc advances one step per day and finishes a full cycle in about 29.5 days. On a fake, a sun and moon disc swaps every 24 hours.
- Set the watch to a known date and note where the moon sits in the window.
- Wait 24 hours. A 24-hour disc moves a full day's worth. A true moon phase moves about 1/29 of the cycle, a shift you can see but not confuse with a flip.
- Find the corrector. Real moon phase watches use a recessed pusher or a dedicated button, not a shared crown position.
Ask the seller for a video of the moon phase over three or four days. A seller with a working complication can send one. A seller with a day/night disc will stall or send a clip that skips the window.
What to Check Before You Buy
- Case size: 43 mm is the correct figure for the Bathyscaphe complete calendar. A 45 mm listing is a different case.
- Crystal: sapphire with anti-reflective coating on better builds. Mineral glass scratches within months.
- Water resistance: many copies leak at the crown. Ask about gaskets and pressure testing, and never swim with an untested replica.
- Calendar pushers: confirm day, date, and month all advance.
- Movement photo: ask for a clear shot of the caseback and the movement name.
- Payment method: use one with buyer protection. Direct bank transfers leave you with no recourse.
Legal and Practical Notes
Replicas of trademarked designs are counterfeit goods in the United States and most of Europe. US Customs and Border Protection can seize a shipment, and reselling a counterfeit watch is a federal offense. Buying one for personal use carries lower risk, but the package can still be stopped and destroyed.
No replica holds value. Service is hard because spare parts do not exist, and a watchmaker may refuse to open a counterfeit. If resale or long-term repair matters to you, a used homage or a Seiko diver is the safer spend.
Frequently Asked Questions
Does a replica Fifty Fathoms Full Moon keep good time?
A mid tier or top tier automatic copy runs within a few seconds to about 20 seconds per day, depending on the movement inside. Budget quartz copies keep time with no fuss but feel light and hollow on the wrist.
How much should a replica Fifty Fathoms Full Moon cost?
Pay $150 to $400 for a copy with a working moon phase and a 43 mm case. Anything under $100 in this model hides a day/night disc in most cases, no matter what the listing claims.
Can a broken moon phase be repaired?
Sometimes, but parts are the problem. Cloned movements share little with the Blancpain 6654, so a watchmaker either sources a replacement movement or leaves the complication frozen. Budget repairs on a $200 watch often cost more than the watch.
Is buying a replica legal in the US?
Importing counterfeit goods violates US customs law, and the item can be seized at the border. Selling is a criminal offense. Personal-use purchases sit in a gray zone that varies by state and by how the seller declares the package.
Which version looks closest to the original?
Top tier builds with a sapphire crystal, a 43 mm case, and a decorated automatic movement come closest at arm's length. The tell is the moon phase window and the dial printing, which stay flat and dull on cheap copies.