Short answer: a Fifty Fathoms replica advertised as "white gold" is almost never solid 18k white gold. At typical replica prices the case is 316L stainless steel with rhodium or white PVD plating, sometimes over a brass core. Solid white gold cases do exist in the modding scene, but they are custom jobs that cost many times what a standard rep runs.
Why sellers say "white gold"
Blancpain builds the Fifty Fathoms in 18k white gold in small batches, usually with a blue dial. The tone is cool and silvery, close to polished steel, so the phrase gets borrowed as shorthand for "white metal finish." Read the listing carefully. If the price is in the low hundreds, the case is steel or a plated alloy, no matter what the title says.
Metal checks that actually work
- Weight. White gold is roughly twice as dense as steel. The same 45mm case should feel about 1.6 to 1.9 times heavier, so a gold Fifty Fathoms on a sailcloth strap would sit noticeably heavier in the hand than a steel one.
- Hallmarks and stamps. Real gold cases carry a purity stamp such as 750 or Au750 plus official Swiss hallmarks. Reps usually leave the caseback clean or engrave something that does not match the real stamping layout.
- Wear pattern. Plating fails first on the lugs, crown guards, and caseback edges. Look for grey steel or a yellow tint bleeding through in those spots.
- Plating can fool an XRF gun. A surface scan only reads the top layer. A density test or an acid test on a hidden area tells you more.
Movement is the bigger giveaway
The genuine 5015 runs Blancpain's calibre 1315, a three-barrel automatic with a 120-hour power reserve and a silicon balance spring. Replicas use decorated ETA clones, Miyota 9015 variants, or a Chinese automatic dressed up with an engraved rotor and fake jewels. The easiest test does not need a caseback tool: wind it fully, set it down, and check it after four or five days. A rep will be stopped. The real thing is still running.
Dial, bezel, and case details
Modern Fifty Fathoms models use a sapphire bezel insert with luminous markers set underneath, which has a depth and slight curvature that painted inserts cannot fake. On the dial, check the applied indices, the printing weight of the Blancpain name, and the date window position for the specific reference you are comparing against. Date wheel fonts on replicas are often too bold or sit too high in the window.
What each price band gets you
- Under $150: plated alloy case, low-beat movement, gritty bezel action, printed bezel markers.
- $300 to $700: steel case, sapphire crystal with decent anti-reflective coating, clone automatic, closer dial and hands.
- $1,000 and up: franken builds with genuine-spec dials, bezels, or hands. Solid gold cases appear here occasionally, and only with paperwork and a jeweller's test to back them up.
Quick checklist before you pay
- Ask for the actual case weight, not just photos.
- Request a clear macro shot of the caseback engraving.
- Confirm the movement family and the power reserve figure in writing.
- Ask whether the bezel insert is sapphire or painted.
- Walk away from anyone calling plated steel "solid white gold."