October 16, 2026

How to Tell If a Cartier Juste un Clou Is Real

By Sasha Tarasova

Filed under Hallmarks, Dating & AuthenticationDesigner & Signed JewelryGold & Precious MetalsBuying Guides

Short answer: a real Cartier Juste un Clou is recognised by precise construction and consistent marks together: a crisply defined nail head and a cleanly finished point in correct proportion, a smooth, even shaft, a solid 18k gold weight that suits the model and size, a discreet opening mechanism that closes firmly, and clean engravings inside including the Cartier signature, a 750 gold mark, the size and a serial number. Final authentication belongs to Cartier or a qualified specialist.

The Juste un Clou is among the most copied bracelets in the world, alongside the Love bracelet it is usually sold beside. Most online advice reduces authentication to "check the serial number", the one feature counterfeiters copy most carefully. This guide covers the history, marks, construction and safe buying. Final authentication belongs to the house or a qualified specialist; we are an independent dealer and not affiliated with Cartier.

Who designed the Cartier Juste un Clou, and when?

The Juste un Clou grew from a nail bracelet designed by Aldo Cipullo for Cartier in New York in the early 1970s. Cartier relaunched the idea in 2012 under the name Juste un Clou, French for "just a nail", and it has been a core collection since.

Cipullo, the Italian-born designer behind the Love bracelet of 1969, took an ordinary hardware nail and bent it around the wrist. The 2012 collection refined the proportions and widened the range to bracelets, rings, necklaces and earrings, in yellow, rose and white gold, with and without diamonds. Our Cartier Love bracelet authentication guide covers the companion piece, and our vintage Cartier jewelry guide places both in the house's wider history.

What does a real Juste un Clou bracelet look like?

A genuine Juste un Clou is a single, continuous nail bent into an oval, with a head at one end and a point at the other, passing each other on the top of the wrist. Every element is in proportion, crisply finished and consistent from end to end.

The nail head

The head is the most scrutinised detail, and the hardest to copy well. On a genuine piece its edges are sharp and clean, its flat surfaces are genuinely flat, and it sits in correct proportion to the shaft. Counterfeits often have a head that is slightly too large or too small, edges softened and rounded by cheap casting and polishing, or a surface that is wavy under a loupe.

The point

The point should taper evenly to a defined, finished tip. It should look deliberate, not blunt and lumpy, and not raw or sharp-edged. On diamond-set versions, the stones on the head and point should be evenly matched, evenly set and level, with neat, consistent beads or claws holding them.

The shaft and profile

The shaft is uniform in thickness all the way round, smoothly polished, and curves in an even oval with no flat spots, kinks or ripples. The head and point should line up as the design intends when the bracelet is closed. The interior is finished as carefully as the exterior. Porosity (small pits in the metal), file marks, visible solder joins and an uneven gap between head and point are signs of a cheaper process.

How does a Juste un Clou bracelet open and close?

How a Juste un Clou opens depends on the model, but on a genuine piece the mechanism is always discreet, works smoothly and closes positively. There should be no rattle, wobble, visible spring or gap once it is shut.

The mechanism is engineering, and engineering is expensive to copy well. Counterfeits often give themselves away with a clasp that is stiff, loose or noisy, that leaves a visible step in the outline, or that does not hold the head and point in alignment. Before inspecting a pre-owned bracelet, read Cartier's own description of the exact model so you know how it is meant to work.

Where are the serial number and hallmarks on a Juste un Clou?

The marks are engraved on the inner surface of the bracelet. Expect, in some combination, the Cartier signature, a gold fineness mark, the size and a serial number, and on pieces made in France, French hallmarks. Exact content and layout vary by model and production.

• Cartier signature. The house name, cleanly engraved, in a font consistent with verified pieces of the same period.
• 750 or Au750. The fineness mark for 18k gold, meaning 750 parts gold per thousand.
• Size. A number corresponding to the bracelet's size. It should match the bracelet's actual measured inner circumference.
• Serial number. A unique number the house can check against its records. Counterfeiters copy genuine numbers, so a serial number proves nothing until Cartier has checked it.
• French hallmarks. On French-made pieces, the eagle's head guarantee mark for 18k gold and a lozenge-shaped maker's mark may appear.

Under a loupe, genuine engravings are crisp, even in depth and evenly spaced, and they follow the curve of the band in a straight line. Shallow, fuzzy, crooked or unevenly spaced lettering is a warning, as is a serial number that also appears in other listings or does not match the paperwork. Our guide to reading hallmarks explains how fineness and guarantee marks work, and why a stamp alone never proves metal content.

Juste un Clou real vs fake: what are the common tells?

Most fakes fail on proportion, finish, mechanism, weight or engravings. High-grade counterfeits in solid gold exist, so no single check settles it; a genuine piece has to be consistent across every feature at once.

Plated fakes

The cheapest copies are gold-plated base metal. They are light, and the plating wears at the head, the point and the inside of the band. A strong magnet catches some steel-core fakes; a firm pull settles the question, but no pull proves nothing, since brass and gold are not magnetic. Our guide on how to tell if gold is real sets out the metal tests that work.

Solid-gold superfakes

Better counterfeits are cast in real 18k gold precisely so that they pass a scale and an acid test. They usually fall down on the head and point, the mechanism and the quality of the engraving. That is why handling by someone who knows verified pieces matters more than any single test.

Does weight tell you if a Juste un Clou is real?

Weight rules fakes out more reliably than it rules genuine pieces in. A plated or hollow copy is usually far too light, but a solid-gold counterfeit can weigh close to the real thing.

Weight also varies with model and size. The classic bracelet, the slimmer small model and the diamond-set versions weigh differently, and a larger size uses more gold. Compare the exact weight in grams on a calibrated scale with verified examples of the same model, size and metal. A seller who will not give an exact weight is withholding one of the easiest checks there is.

Are box and papers proof that a Juste un Clou is real?

No. Red Cartier boxes, certificates, pouches and receipts are all reproduced, and genuine packaging is sold separately to be paired with counterfeits. Paperwork supports provenance; it does not prove authenticity.

Paperwork carries weight only when it can be verified: a receipt from a named Cartier boutique that you can check, a certificate whose serial number matches the bracelet exactly, or house service records. Treat any paperwork you are not allowed to verify before paying as decoration. The wider logic of signatures and provenance is covered in our guide to signed vs unsigned jewelry.

Where are fake Juste un Clou bracelets most common?

Fakes are most common wherever a buyer cannot handle the piece and the seller cannot be held to account: open marketplaces, social media sellers, private sales arranged through messaging apps, and listings priced well below the secondary market.

A nail-shaped bracelet by another maker, sold under its own name, is a design homage, not a counterfeit; it becomes a fake when it is marked or sold as Cartier. And a "Cartier" offered far below the secondary market is stolen, misdescribed or not genuine, whatever the story. Our guide to buying jewelry online safely covers the wider patterns.

Vintage 1970s nail jewelry connected with Cipullo is a separate, rare and specialist area; claims about it deserve examination by someone who has handled documented examples.

How do you buy a pre-owned Juste un Clou safely?

Buy the seller first. The safest pre-owned Juste un Clou comes from a seller who authenticates before listing, states the model, size, metal and weight in writing, and offers a return window long enough for independent verification.

1. Confirm the model: classic, small model or diamond-set, and the metal colour.
2. Ask for the exact weight in grams and compare with verified pieces of the same model and size.
3. Ask for sharp photographs of every engraving in natural light.
4. Examine the head and point under 10x magnification for crisp edges and correct proportion.
5. Check the mechanism on video: it should open smoothly and close firmly, with no play.
6. Measure the inner circumference and confirm it matches the engraved size.
7. Verify paperwork independently and match serial numbers between paper and bracelet.
8. Get a written authenticity guarantee with a full refund if Cartier or an independent authenticator disagrees.
9. Pay with buyer protection, and have the piece examined within the return window.

Our note on what a dealer should disclose sets out what a straight seller will put in writing.

Where can you authenticate a Cartier Juste un Clou?

The definitive check is Cartier itself, through its boutiques. The next best is an experienced independent specialist in signed jewelry who examines the physical piece, has no stake in the sale and puts findings in writing.

A Cartier boutique will accept a piece for service, and the house examines what it services. Services and fees change, so ask what is currently offered, and expect the piece to be sent away rather than assessed across the counter. Photo-only authentication can catch crude fakes; it cannot reliably catch a superfake. Once a genuine piece is yours, schedule it on an insurance policy with a current appraisal and photographs of the engravings; our guide to insuring jewelry explains why.

Questions people actually ask

How can you tell if a Cartier Juste un Clou is real?

Check that the nail head has crisp edges and correct proportions, the point tapers to a clean finished tip, the shaft is even, the mechanism closes firmly with no play, the weight suits the model and size, and the engravings inside are crisp and consistent. Then confirm with Cartier or a qualified specialist who handles the piece. No single feature proves authenticity on its own.

Where is the serial number on a Juste un Clou bracelet?

The serial number is engraved on the inner surface of the bracelet, together with the Cartier signature, a 750 gold fineness mark and the size, and on French-made pieces sometimes French hallmarks. Layout varies by model and production. The number is useful mainly in Cartier's hands, because the house can check its records, while counterfeiters routinely copy genuine serial numbers.

Who designed the Cartier Juste un Clou?

The Juste un Clou is based on a nail bracelet designed by Aldo Cipullo for Cartier in New York in the early 1970s. Cipullo also designed the Love bracelet, introduced in 1969. Cartier relaunched the nail design in 2012 as the Juste un Clou collection, which now includes bracelets, rings, necklaces and earrings in several colours of 18k gold.

Can a fake Juste un Clou be made of real gold?

Yes. High-grade counterfeits are sometimes cast in solid 18k gold so they pass a scale and an acid test. They usually give themselves away in the nail head and point, the opening mechanism and the quality of the engraving. That is why weight is a necessary check but not a decisive one, and why in-person authentication by a specialist matters.

Is a nail bracelet from another brand a fake Cartier?

Not necessarily. A nail-shaped bracelet made and sold under another maker's own name is a design homage, not a counterfeit. It becomes a fake when it carries Cartier marks or is described and sold as Cartier. Buyers should still be clear on what they are paying for, since such pieces have none of the value of a genuine Cartier.

Do box and papers prove a Juste un Clou is genuine?

No. Cartier boxes, certificates, pouches and receipts are reproduced, and genuine packaging is sold separately for pairing with counterfeits. Paperwork only adds weight when it can be verified: a receipt from a named boutique, a certificate whose serial number matches the bracelet, or house service records. Authenticate the bracelet itself, not the box it arrives in.

Will Cartier authenticate a pre-owned Juste un Clou?

Cartier boutiques accept pieces for service, and the house examines what it services and will not service a counterfeit. Services, timelines and fees change, so ask your boutique what it currently offers. Expect the piece to be sent to the house rather than checked on the spot, and keep any written findings with your insurance records.

We handle signed jewelry regularly and authenticate before anything is offered; you can browse our signed and designer jewelry. If you want a Juste un Clou in a particular model, size or metal and would rather not do the checking yourself, our sourcing service finds and verifies signed pieces before you commit. More guides of this kind sit in our authentication archive.