That blue box you inherited. The Cartier Love bracelet you found in a drawer while cleaning out your parents’ house. The Van Cleef necklace your grandmother said was the real thing. Before you wear it, insure it, or sell it, you want to know: is it actually authentic and what is it really worth?

Counterfeit luxury jewelry is a multibillion-dollar global industry. At the same time, genuine signed pieces from the top houses routinely sell for two to four times what the same stones and metal would fetch in unbranded form. That gap is exactly why fakes get made, and exactly why authentication matters before you make any decision to sell a piece.

This guide walks through how to check the authenticity of jewelry of the most commonly counterfeited pieces as well as red flags to spot fakes:

•  Tiffany & Co
• Cartier
• Van Cleef & Arpels, 
• Harry Winston,
• Bulgari

What are universal authentication basics?

There are five things to check on any signed piece from the major brands:

1. Real signed jewelry will have hallmarks and metal stamps

Real signed jewelry is almost always stamped with the metal purity. For gold, that means 750 (18K), 585 (14K), or 375 (9K) or the word “18K,” “14K,” etc. For silver, look for “925” or “Sterling”. Platinum is stamped “PT950” or “Platinum”. A piece with no metal stamp should be approached with caution, unless it’s a very old antique piece before hallmarking norms were standardized.  Any standard magnifying glass or your smart phone camera will help you locate these markings

2. Look for maker’s mark and signature

Every major house signs its work. The signature is usually crisp, stamped evenly, and in a specific font the brand has used for decades. Fuzzy, crooked, or inconsistent lettering is one of the clearest signs of a counterfeit.

3. Serial numbers stamped

Cartier, Van Cleef, Harry Winston, and most houses stamp a unique serial number on each piece. The number should be small, precise, and in a font consistent with the brand. If there is no serial number at all on a piece that should have one, that is a major red flag.

4. Weight and feel should be heavier than they look

Real gold and platinum pieces feel substantially heavier than they look. Counterfeiters cut corners by using hollow construction, base metals, or thin gold plating which makes pieces feel noticeably lighter. If a piece feels cheap in your hand, it probably is.

5. Craftsmanship quality

Look at the back of the piece, inside the clasp, and where two components meet. Real signed jewelry is finished beautifully on every surface, even the ones you don’t see. Counterfeit pieces typically have rough edges, uneven soldering, and visible tool marks in places an original maker would never leave due to their high quality standards in finishing pieces.

If all five of these pass a careful inspection, the piece is probably real. If any one of them fails, be cautious if considering a purchase.

How to authenticate Tiffany & Co.

Tiffany is one of the most commonly counterfeited jewelry brands. Here is what to look for:

The Tiffany stamp. Genuine Tiffany silver is stamped either “TIFFANY & CO.” (block letters, precise spacing) or just “T&Co.” The lettering should be clean and consistent. On silver, you’ll also see “925” or “Ag 925.” The word “STERLING” may or may not appear; its absence is not necessarily a red flag on older pieces.

Font and depth and fingernail test. Tiffany uses a specific font.  The letters have an almost hand-stamped quality on older pieces and a cleaner machine-struck look on newer pieces. The stamps are deep enough to feel with a fingernail but never sloppy or uneven. Stamps that look “printed” rather than struck are counterfeits.

Designer signatures. Many Tiffany pieces also bear a designer’s signature in script — Elsa Peretti, Paloma Picasso, or Jean Schlumberger. These signatures are crisp and stamped into the metal. A designer name in printed ink or an overly shiny decal is a fake.

The chain and clasp. Genuine Tiffany chains feel substantial and smooth. The clasp is usually stamped “Tiffany & Co.” in miniature — a detail counterfeiters frequently miss. If the clasp is blank or marked with a generic brand, the piece is suspect.

The box and pouch. The famous Tiffany Blue Box is a specific shade (Pantone 1837) with a white ribbon. The pouch inside is a microfiber, not a rough felt. Boxes and pouches alone do not prove authenticity, but a piece that came with obviously wrong packaging is not a good sign.

How to authenticate Cartier

Cartier pieces, especially the Love bracelet, Juste un Clou, and Trinity ring, are among the most faked items in the world. Authenticating them well is harder than Tiffany because Cartier’s work is more complex.

Signature and serial number. Every authentic Cartier piece is signed “Cartier” in a specific cursive script and stamped with a unique serial number. On the Love bracelet, the signature and serial are on the inside of the band. The font is important as counterfeiters frequently get the cursive slightly wrong, with letters too thick, too thin, or spaced inconsistently.

Hallmarks. Cartier uses 18K gold (stamped “750”), platinum (stamped “PT950”), and sometimes 950 palladium. In addition to the metal mark, you’ll often find a small assay stamp (the French “eagle head” for 18K gold, for example) and a tiny maker’s mark specific to Cartier.

Screw alignment on the Love bracelet. The iconic Love bracelet’s screws should be perfectly aligned when closed and turn smoothly with Cartier’s proprietary screwdriver. Counterfeits often have screws that are slightly off-axis, feel loose, or strip when you try to turn them.

Weight. Real Cartier Love bracelets weigh approximately 30–35 grams depending on size. Fakes are often 5–10 grams lighter.

Certificate and box. Modern Cartier pieces come with a certificate of authenticity listing the serial number, which matches the stamp on the piece. The red box is specific, a deep red with “Cartier” in embossed gold. Missing paperwork does not prove a fake as pieces passed down through generations often lose their papers, but mismatched paperwork is a red flag.

How to authenticate Cleef & Arpels

Van Cleef is more understated in its markings than Cartier. The Alhambra collection is one of the most copied.

Signature. Authentic Van Cleef pieces are stamped “VCA” or “Van Cleef & Arpels” in very small, very crisp letters, usually on an inconspicuous surface, on the back of a clover, inside of a clasp, or the edge of a ring band.

Serial number. Every Van Cleef piece has a unique serial number, typically near the signature. The number is small, evenly spaced, and precisely struck.

Mother-of-pearl and stones. On Alhambra pieces, the mother-of-pearl inlay has a specific iridescent quality. A real mother-of-pearl shifts color as light hits it at different angles. Plastic or resin imitations look flat. Onyx, chalcedony, and malachite versions should show natural stone variation, never the perfect uniformity of a manufactured material.

Gold color and finish. Van Cleef yellow gold has a distinct warm hue, and their white gold and rose gold are similarly consistent. Off-color pieces that are brassy, pale, or too pink often indicate plated low-karat fakes.

Hardware. The pin and clasp on an Alhambra necklace should work smoothly and feel solid. Flimsy clasps and chains that tangle easily are signs the piece is not right.

Other quick ways to assess other top brands:

Harry Winston. Signed “HW” or “Harry Winston” with a serial number. Pieces are typically platinum with high-grade diamonds (usually D-F color, VS1 or better clarity). If the stones look dull or yellowish, the piece almost certainly isn’t genuine Harry Winston.

Bulgari. Signed “BVLGARI” (with the V, their stylized Roman spelling) and a serial number. The Serpenti and B.zero1 collections are heavily counterfeited. Look for precise enamel work, evenly set stones, and substantial weight, a sign of an authentic piece.

Graff. Signed “Graff” with paperwork specifying the stone quality. Graff pieces are typically set with large, exceptional-quality diamonds. Without accompanying paperwork from Graff, resale value falls substantially. Authentication by the house or a top lab is essential.

David Yurman. Signed “D.Y.” or “David Yurman” with a sterling silver or gold hallmark. Yurman is more accessible than the others, but the cable motif and quality of stone setting are strong tells for authenticity.

Red flags that scream counterfeit:

If you see any of these, be very suspicious — even if the rest of the piece looks right:

• Misspelled signatures. “TIFFANY & Co” with the wrong capitalization, “Cartyer,” “Van Cleef & Arpeles.” Counterfeiters make mistakes.
• Wrong metal stamp. A piece that claims to be solid 18K gold but is stamped “925” is sterling silver (or gold-plated silver), not gold.
• Magnetism. Real gold, silver, and platinum are not magnetic. If a magnet sticks, the piece contains base metal and is not what it claims to be.
• Discoloration at wear points. Gold and platinum do not tarnish, and real plating on quality pieces lasts decades. If you see silver or copper showing through at the clasp or edges, the piece is plated, not solid.
• Price history. If the piece was purchased for a suspiciously low price from a non-boutique source, especially online, the odds of it being a fake are high.

What To Do If You Can’t Tell

Authentication is harder than it looks, especially on older pieces where markings have worn or been polished off, and on modern counterfeits that have become remarkably sophisticated. The stakes are real: misidentifying a $10,000 Cartier piece as scrap costs you thousands; treating a convincing fake as genuine leads to disappointment when you try to sell.

Professional authentication is fast, usually free as part of a valuation, and takes most of the guesswork off your plate. A qualified buyer has seen thousands of examples of each major brand, owns testing equipment most individuals don’t, and can tell you both whether the piece is real and what the current market offer would be.

Ready for a free authentication and offer? 

Bring your piece to DNR Diamonds in Chicago or New York, or send us photos online filling out the form below for a same-day response.  We have been assessing signed pieces since 1994 with many happy customers. Whether you decide to sell today, next month, or not at all, you’ll walk away knowing exactly what you own.