The short answer
A fake Fifty Fathoms chronograph is almost never a copy of a real Blancpain chronograph movement. Most are a generic chronograph case with a Fifty Fathoms style dial dropped into it, and the better ones use an off-the-shelf Swiss or Japanese caliber instead of anything in-house. The fastest way to tell them apart is the flyback function. The genuine Bathyscaphe Chronographe Flyback resets and restarts with one push of the lower button, no stop, no restart. Copies essentially never do this properly.
What the real watch is
Blancpain put the modern dive watch on the map in 1953 with the Fifty Fathoms. The chronograph version most people picture is the Bathyscaphe Chronographe Flyback: a 43.6mm case, 300m of water resistance, a ceramic bezel insert, and the in-house F385 caliber with a column wheel, vertical clutch, silicon balance spring, and a 5 Hz beat rate. That is a lot of engineering to fake, which is why nobody seriously tries at the movement level. The copies fake the outside, not the inside.
Tells you can catch in a photo
- Date position. Many Fifty Fathoms dials set the date at 4:30. Copies park it at 3 because that is where the donor movement puts it.
- Subdial spacing. On the genuine, the counters sit close to the center. Copies spread them wide or shrink them to hide the gap.
- Bezel scale. Check the font weight and the shape of the 15, 30, and 45 numerals, and whether the markings sit flush or look painted on top.
- Caseback engraving. Depth rating, model name, and serial should be crisp and correctly placed, not a shallow laser etch with fuzzy edges.
- Crown and pushers. Pusher travel should feel firm and short. Cheap ones grind and travel too far.
- Case profile. The genuine midcase is stepped, with defined lugs. Copies are slab-sided and often thicker than the listed specs.
What is actually inside the copies
- Quartz or budget automatic. The subdials are decorative or glued on, the chronograph does not function, and "Swiss Made" is printed with no Swiss involvement at all.
- Asian chronograph movements. Seagull ST19 and 7750 clones give you real chronograph function, but no flyback, no column wheel, a slower beat rate, and rotor engraving that does not match the real caliber.
- Decorated clones. Closer case and dial work, movement still wrong, and the extra thickness is usually what gives it away on the wrist.
Why the Swiss Made stamp means little here
Swiss law sets strict conditions before a watch can carry that label, and counterfeiters print it regardless of where the parts came from. The same goes for dive watch claims. ISO 6425 is the international standard for divers' watches and covers water resistance testing and legibility. Replicas are not tested to it, and the sellers who claim otherwise are quoting a standard they have never met.
Where the legal ground sits
Counterfeit watches infringe trademarks, and importing or selling one is illegal in the US and across most of the EU. Buying one for personal use carries lower risk, but it is not zero, and customs seizures do happen. Price is another honest signal. A genuine F385 flyback chronograph runs into five figures, so anything advertised with matching specs at a tiny fraction of that is not the same watch no matter how the listing is worded.
Quick checklist before you decide
- Does the chronograph actually run, and does the lower pusher do anything?
- Is the date window at 4:30 or at 3?
- Does the case measure what the listing claims?
- Are the bezel numerals the right shape, not just the right number?
- Does the movement engraving match a caliber Blancpain actually makes?
If two or three of those fail, you are looking at a costume piece, not a replica of anything.