Short answer
A fake Fifty Fathoms 5050 is a replica of the Blancpain Fifty Fathoms Automatic, a 45 mm dive watch with a sapphire bezel and the in-house caliber 1315. Replica versions come in three rough tiers: budget builds under about $150 with quartz or low-grade automatic movements, mid-tier builds from $200 to $450 with a Seiko or Miyota movement and a sapphire crystal, and high-end builds above $500 that copy the case shape, dial print, and bezel action but rarely the movement. None of them match the genuine watch on finishing, water resistance, or service life.
What the genuine 5050 does
The 5050 is a 45 mm diver in steel or titanium with 300 m of water resistance. Blancpain fits the in-house caliber 1315, a three-barrel automatic with a 120 hour power reserve. The bezel insert is sapphire with lume markings underneath, the crystal is domed sapphire, and the dial uses broad sword hands with applied markers. Case flanks are polished and the lug tops are brushed. Those are the details a replica has to match, and the bezel and the power reserve are the two that most copies fail.
Replica tiers for the 5050
Budget tier (under about $150)
A quartz module or a low-grade automatic, mineral glass, painted markers, and a bezel that wobbles when you press it. Case width often lands at 43 mm or 46 mm instead of 45 mm. Lume dies in twenty minutes. These are the easiest to spot from two feet away.
Mid tier ($200 to $450)
Seiko NH35 or Miyota 9015 inside, sapphire crystal with a single AR coat, and a case with decent brushing. The bezel insert is usually glass or coated plastic rather than sapphire. Dial text sits close but stroke weight drifts. Power reserve lands near 40 hours. This tier looks correct in a seller photo and less correct on a wrist.
High-end tier ($500 and up)
Correct 45 mm dimensions, sapphire bezel insert, applied markers with clean lume fill, and a movement with decorated bridges that copies the look of the 1315. Builders use a modified Asian 2836 or a custom clone. Power reserve still falls short of 120 hours. Date font and window cut are common giveaways, and water resistance testing is a claim, not a certificate.
How to check a replica before you buy
- Ask the seller for the exact movement reference and a clear photo of the rotor and balance wheel.
- Measure the case with calipers and confirm 45 mm across, crown excluded.
- Tap a fingernail on the bezel insert; sapphire rings sharper and feels colder than glass or plastic.
- Inspect dial text under a loupe and compare letter spacing in "Fifty Fathoms" against a reference photo.
- Wind the crown fully, set it down, and time how long the watch runs over the next 24 hours.
- Measure the lug width and confirm the seller stocks straps in that size.
- Request photos of the caseback engraving and serial, since misaligned text is common on low-tier builds.
- Treat any water resistance claim above 100 m as unverified until a watchmaker pressure tests the case.
Legal notes and daily use
US Customs and Border Protection can seize counterfeit watches at import, and the FTC treats selling a replica as a genuine watch as trademark infringement. Buying one for personal use is a different matter from selling, but the shipment itself can still be stopped. If you own a replica, keep it out of the water until a watchmaker replaces the gaskets and pressure tests it. Expect no service support from Blancpain or any authorized center, and budget for a movement swap if the original unit fails.