Short answer
A 45mm fake Fifty Fathoms copies Blancpain's Fifty Fathoms Automatique, the biggest of the modern Fifty Fathoms dive watches. The better replicas get the case size, the dial layout and the sapphire bezel close enough to fool someone across a table. They give themselves away in three places: the movement, the bezel click, and the lume. Check those first and you will know what you are holding.
What the genuine 45mm is
Blancpain put the Fifty Fathoms on the market in 1953, built for French combat swimmers, and it set the template that most dive watches still follow. The modern Automatique takes that design and scales it up. The case runs 45mm across and roughly 15.4mm thick, water resistant to 300 metres, with a screw-down crown and a sapphire bezel insert on a steel or titanium case. Inside sits the in-house caliber 1315, a three-barrel automatic with a 120 hour power reserve and a silicon balance spring. The dial carries the Blancpain signature at twelve, Fifty Fathoms above six, and a date window at three. Steel references like the 5015-1130-52A are the ones most often copied.
Where the replicas hold up
Case dimensions are easy to copy and most factories do it well. A good 45mm replica measures within a fraction of a millimetre of the real thing and takes the same strap lugs, so aftermarket Fifty Fathoms straps and the genuine sailcloth strap both fit. Dial printing has improved a lot in the last few years. The Blancpain wordmark, the Fifty Fathoms text and the AUTOMATIQUE line are usually crisp on the upper tier replicas, and the applied markers sit at the right height. The sapphire bezel insert is the single best feature on the better copies. Real ones use a sapphire ring with the lume printed underneath, and the replica version gets the depth and refraction close.
The tells that matter
I look at four things before anything else.
- The bezel action. The genuine bezel turns with a firm, even, 120 click feel and zero back play. Replicas tend toward either a gritty grind or a mushy free spin with slop in the ring.
- The lume. Genuine Super-LumiNova glows evenly across the bezel pip, the hour markers and the hand tips. Copies often glow brighter on the hands than on the dial, or fade within twenty minutes.
- The case back. The Automatique has an exhibition back. A replica movement under that crystal is where the illusion dies, so look for engraved bridges and a rotor finish that does not match the real 1315.
- The date. On the real 5015 the date disc is black with white numerals, well centred in the window. Crooked or grey-ish date wheels are common on cheaper builds.
Movements, honestly
Nobody is putting a real 1315 in a replica, and anyone who says otherwise is selling something. What you actually get is a Japanese Miyota 9015, a Chinese clone of an ETA 2824, or a decorated movement with fake bridges screwed on top to look like the Blancpain caliber. The decorated ones photograph well and service badly. A Miyota based build is the safer bet if you plan to wear it daily, because any decent watchmaker can regulate it and parts exist. Expect around 40 hours of power reserve, not 120.
How 45mm actually wears
Forty five millimetres sounds enormous. On the Fifty Fathoms it works, because the bezel is broad, the lugs curve down, and the whole thing sits flat rather than tall. If your wrist is under about 6.75 inches, it will overhang and look like a borrowed watch. Wrist size matters more than the number on paper. Measure your wrist, then subtract a couple of millimetres if you plan to wear it on a rubber strap, which adds height.
The practical side
These are unauthorised copies of a trademarked design. Buying one is legal in some places and not in others, and importing one can mean seizure at customs with no refund. No Blancpain service centre will touch it. Resale value is near zero the moment it leaves the box, and the forums are full of people who paid too much for a mid tier build. That is the trade you are making, and it is worth going in with your eyes open.
What to check before you commit
- Ask for a video of the bezel turning, not a still photo.
- Ask for a lume shot taken in the dark, with a timestamp.
- Ask which movement is inside, by name. Vague answers mean a decorated clone.
- Confirm strap width at the lugs, usually 23mm on this reference.
- Check the return policy in writing before payment, because most are final sale.