What Is a Fake Fifty Fathoms Full Moon?
A fake Fifty Fathoms Full Moon is a third-party copy of the Blancpain Fifty Fathoms Bathyscaphe Quantième Complet Phases de Lune, a dive watch that pairs a full calendar with a moon phase at 6 o'clock. The real watch shows day and month in windows, a serpentine date hand on a numbered track, and a lunar disc that turns once every 29.5 days. That stack of complications is the reason this model is hard to copy well, and the reason the moon phase is the first thing to inspect.
Does the Moon Phase Actually Work on a Replica?
On most replicas, no. A large share use a 24-hour disc that rotates once a day, so the moon crosses the aperture overnight instead of over a month. Mid and top tier replicas sometimes use a true moon phase gear linked to the calendar, and those track the real lunar cycle.
- Static moon: a printed disc that never moves. Common on quartz versions.
- Day/night disc: the moon moves once per day. This is the most common fake setup.
- True moon phase: 29.5-day cycle, set with a corrector or pusher. Found on better automatics.
To test it, note the moon position, wait 24 hours, and check again. A real lunar disc shifts by a small sliver. A day/night disc jumps to the other side of the aperture.
How Do You Spot a Fake Fifty Fathoms Full Moon?
Work through the complication first, then the case, then the printing. Replica makers spend money on the outside and cut corners on the calendar mechanism, so the tells cluster around the dial layout.
1. Check the calendar layout
Blancpain's complete calendar uses a serpentine date hand that points to a numbered track around the dial, with day and month in windows near 12. A replica that shows a plain date window at 3 o'clock is wrong before you look at anything else. On many fakes the day and month windows sit too far apart, or the text inside them is printed at the wrong weight.
2. Look at the moon disc itself
The genuine moon is a raised, hand-finished face on a dark blue disc with stars. Replicas often print a flat circle that reads as a sticker under a loupe. Color is another giveaway: real discs sit in a deep blue, while fakes lean toward purple or flat black.
3. Inspect correctors and case sides
Genuine Blancpain calendars use recessed correctors that sit flush with the case, not exposed pushers sticking out of the band. If you see four or five protruding buttons on the side of a Fifty Fathoms, that is a copy. The Bathyscaphe line also keeps clean flanks, so any clutter stands out.
4. Turn it over
The caseback and rotor show the gap in finishing. Real Blancpain movements carry Geneva stripes, polished bevels, blued screws, and crisp engraving. Replicas show stamped rotor text, dull brushing, and screws with soft slots.
5. Check the bezel, crown, and crystal
The Bathyscaphe bezel insert is sapphire with lume under the surface, which gives depth and a slight dome. Fakes use printed ceramic or coated glass that looks flat. The crown should be signed, sit tight against the case, and turn with a smooth click at each position.
What Movement Sits Inside a Replica Fifty Fathoms Full Moon?
Most run a Chinese automatic built on a Valjoux 7751 layout or a 2824 with a calendar module bolted on top. The 7751 family gives day, date, month, 24-hour display, and moon phase from one base, which is why it appears in so many calendar replicas. The genuine watch uses an in-house Blancpain caliber, and no replica matches it at the component level.
That matters for service. A module-based replica can be repaired by any watchmaker who works on Asian movements, while a 7751 clone has parts that are easy to source. Ask what movement is inside before you buy, and expect a printed answer or none at all.
What Does a Replica Fifty Fathoms Full Moon Cost?
Prices sit in three rough bands, and the moon phase is what separates them. These are typical marketplace ranges, not fixed prices, and sellers move them often.
- Under $100: quartz or basic automatic, static or day/night moon, thin plating, poor dial print.
- $150 to $350: automatic with a working moon phase on some units, sapphire crystal, better case finishing.
- $400 and up: modified 7751 or clone with true lunar gearing, closer dial layout, solid bracelet or strap hardware.
What Should You Check Before Buying?
- Ask for a video of the moon phase moving, filmed 24 hours apart if possible.
- Confirm the date is shown by a hand, not a window.
- Ask for the movement name and whether a corrector tool comes with the watch.
- Request close photos of the case flanks, caseback, and dial text.
- Check the water resistance claim. A calendar watch with a dive case is not built to dive.
- Read the return policy before payment, since calendar faults show up in the first week.
Common Mistakes Buyers Make
The biggest one is judging from one glossy photo. Dial print, moon disc color, and bezel depth disappear in marketing shots taken under soft light.
Another is setting the calendar at the wrong time. Never change the day, month, or moon when the watch reads between roughly 9 p.m. and 3 a.m., because the gears are mid-shift and can jam. Replicas use softer metal than the genuine article, so this damage is permanent.
Buyers also forget that a full calendar needs resetting after months with fewer than 31 days. That is true of the real Blancpain too, and it is not a defect.
FAQ
Is a replica Fifty Fathoms Full Moon worth it?
It depends on what you want. If you want the calendar look and a working moon phase, a mid tier automatic delivers that for a fraction of the real price. If you want accuracy, parts support, and resale value, no replica provides any of the three.
Can a jeweler tell it is a fake?
Yes, and fast. The moon disc, the date hand, and the caseback finishing are visible without opening the watch. Any watchmaker who handles Blancpain regularly will spot a copy in seconds.
Does the moon phase need setting?
On replicas with a true lunar gear, yes. You set it to the current phase using a corrector or the crown, then adjust after months when the calendar is out of step. On day/night versions there is nothing to set because the disc is not a lunar display.
What size is the replica?
Most copies follow the Bathyscaphe Quantième Complet at 43 mm, with some 38 mm versions on the market. Measure your wrist before ordering, because a calendar dial plus a dive bezel reads large on a small wrist.