Short answer
A fake Fifty Fathoms sold as 43mm copies the mid-size case of the Blancpain line. The genuine Fifty Fathoms Automatique 5015 measures 45.0mm. The Bathyscaphe measures 43.6mm. Blancpain added a 42.3mm Automatique in 2023. Replica sellers round these numbers to 43mm. Ask for caliper photos across the case at 3 o'clock and 9 o'clock, plus thickness measured off the caseback, not the crystal.
Genuine sizes for reference
- 5015 Automatique: 45.0mm diameter, 15.4mm thick, 300m rating
- Bathyscaphe 5000: 43.6mm diameter
- Automatique 42.3mm: 42.3mm diameter, 14.0mm thick
Replica cases land between 42.5mm and 43.5mm. Thickness runs 13.5mm to 16mm. Most builds use 316L stainless steel. A small number use 904L. Case weight sits near 95g to 105g on rubber and 150g to 170g on a steel bracelet.
Movement inside
The genuine runs Caliber 1315. Three barrels give a 120-hour power reserve. The balance spring is silicon. Replica movements split by tier. Entry builds use a Miyota 9015 or a Seagull ST2130 with a printed rotor. Mid builds use a Hangzhou 6-series or a modified ETA 2824. High tiers use a decorated clone with a 100-hour to 120-hour reserve claim. Reserve claims from sellers go unverified. Time the watch across 24 hours on a full wind.
Bezel, crystal, dial
The genuine bezel insert is sapphire with Super-LumiNova markers. Replica inserts come in three grades. Printed acrylic sits at the bottom. Mineral glass sits in the middle. Sapphire copies sit at the top. Crystal is sapphire on mid and high tiers. Anti-reflective coating appears on both faces on high tiers and one face on mid tiers. Dial text, date font, and the Blancpain script vary in stroke weight. Genuine dials use applied markers with polished edges.
Lume
Genuine watches use Super-LumiNova. Replica lume grades include C3, C1, and unbranded powder. C3 glows green. Charge the watch under a lamp for 60 seconds and check after 30 minutes. Weak lume fades in under 20 minutes.
Water resistance
No replica carries a manufacturer depth test. Sellers list 50m to 300m ratings. Gaskets, crown tube fit, and caseback torque decide the real number. Pressure-test any replica before water contact. A watchmaker charges $20 to $40 for a dry test. Skip the test and treat the watch as splash-resistant.
Prices by tier
- Entry: $80 to $180
- Mid: $220 to $420
- High: $450 to $800
Price tracks movement grade, insert material, and bracelet finish. Ask for a movement photo before payment. Serial numbers on replicas repeat across batches. Genuine 5015 serials are unique and traceable through Blancpain service. No public data exists on the failure rate of clone 1315 movements.
Checks on arrival
- Measure case diameter at 3 and 9 o'clock with calipers.
- Turn the bezel: 60 clicks, no back play.
- Watch the date change. It should flip at midnight, not 23:30.
- Time the watch for 24 hours against a reference clock.
- Charge the lume for 60 seconds, then check glow after 30 minutes.
Legal note
Counterfeit watches infringe trademarks. US Customs seizes replica shipments under 19 CFR 133.21. Resale of counterfeit goods is a federal crime in the US under 18 U.S.C. 2320, with penalties up to 10 years for a first offense.