Gold and Silver Hallmarks and Stamps Decoder

The tiny stamps inside a ring band, on the clasp of a chain, or on the underside of a spoon do a specific job: they encode what the metal is, sometimes who made it, sometimes when and where it was tested. Most people never notice these marks until a piece is being sold, appraised, insured, or handed down. At that moment, decoding them becomes suddenly useful.

Two parallel systems handle most of the world’s precious metal marking. The karat system (used in the United States and much of the English-speaking world) records fineness on a 24-part scale. The millesimal system (used across Europe and increasingly in international commerce) records fineness in parts per thousand. This guide walks through both, adds the specialized codes for silver, platinum, and gold-plated goods, and covers the country hallmark systems most likely to appear on jewelry sold in the United States.

The Karat System: What the K Numbers Mean

Gold in its pure form is too soft for most jewelry uses. It scratches, bends, and deforms under daily wear. Manufacturers alloy it with copper, silver, zinc, nickel, or palladium to add hardness and to shift color (yellow, rose, white). The karat number records how much of the finished alloy is gold, on a scale where 24 karat equals pure gold.

The most common karat marks and their corresponding purities are shown in the table below.

In the United States, the National Stamping Act (15 USC 291 to 300) sets 10 karat as the minimum to legally sell an item stamped as “gold.” Marks below that threshold appear on imported pieces but should never claim to be gold outright without qualifying language. The stamp variations (K, KT, or nothing after the number) all mean the same thing.

Fractional Marks on American Gold-Filled Pieces

American vintage costume jewelry frequently carries marks like “1/20 12KGF” or “1/10 14KGF.” These are fractional gold-filled marks. The fraction is the weight of the gold alloy layer expressed as a proportion of the finished piece; the karat number is the fineness of that layer. A 1/20 12KGF chain has a 12 karat gold outer layer that equals at least 1/20 of the total weight. This is covered in the plated and filled section below.

The Millesimal System: 999, 750, 585 Explained

Continental European and modern international marking uses a three-digit number representing parts per thousand. This system is more precise than karat marks because it captures fractional purities that the whole-number karat scale rounds. The same information appears on many American pieces too, especially those imported or made after roughly 1980.

Read the number in context. A stamp of 925 on a silver-colored ring is sterling silver. A stamp of 950 on a white-metal wedding band is almost certainly platinum. A stamp of 750 on a yellow band is 18 karat gold. If the color and the number seem to disagree, the piece may be plated or the mark may be misapplied; testing beyond the stamp becomes worthwhile.

Silver Marking Standards

Silver has more named standards than gold because silver has been used for currency, hollowware, and jewelry across many national traditions. The main marks a US reader will encounter are covered below.

Sterling and Fine Silver (US and International)

Under the Federal Trade Commission’s Guides for the Jewelry, Precious Metals, and Pewter Industries (16 CFR Part 23), a piece may be marked “sterling,” “sterling silver,” “925/1000,” or “.925” only if it contains at least 925 parts silver per 1,000. The word “coin” or “coin silver” is reserved for at least 900 parts per thousand. Fine silver bullion is 999 parts per thousand or higher.

Britannia (UK Historical, Still in Use)

Britannia silver was introduced in England in 1697 at 958 fine (95.8% silver) to discourage the melting of coinage into flatware. Modern UK hallmarking still recognizes the Britannia standard, marked with a seated Britannia figure alongside the 958 numeral.

800 and 830 Continental Silver

800 silver is the traditional standard across much of continental Europe, particularly Germany, Austria, and pre-1968 Italy. It contains 80% silver with 20% copper. Scandinavian pieces (Denmark, Norway, Sweden, Finland) often carry an 830 mark, sitting between 800 and sterling. Both are legitimate precious metal alloys but sit below the US “sterling” threshold, so a US resale price reflects their lower silver content.

Coin Silver

American pieces from the 18th and 19th centuries frequently carry the mark “COIN” or “PURE COIN,” indicating an alloy of approximately 900 fine (90% silver), the composition of US coinage of the era. Coin silver flatware and hollowware from established American silversmiths carry both metal value and collector interest.

Platinum Marks: PLAT, PT950, and Lower Alloys

Platinum’s density and cost make it the premium metal for engagement rings and high-end watches. Marking is regulated in the United States under an amended National Stamping Act that treats “platinum” as a term of quality, not a color descriptor.

A ring marked only “Platinum” or “PLAT,” with no qualifying number, must contain at least 950 parts platinum per thousand under US rules. Lower-purity alloys are required to state the fineness (for example PT900) and identify the other platinum-group metal used. This is why many older engagement rings show IRIDPLAT: it declared both the platinum content and the iridium hardener.

Plated, Filled, Vermeil, and Overlay: The Non-Solid Codes

A significant share of jewelry sold as “gold” is not solid gold. Federal Trade Commission rules under 16 CFR Part 23 define specific terms that describe how the gold layer is applied, how thick it is, and what sits underneath. Understanding these codes prevents overpaying for costume jewelry and clarifies what a piece is actually worth at buyback.

The practical rule for scrap or resale value: only solid gold (10K and above without a fraction prefix) and solid silver (925 or higher, or the recognized 800 to 900 continental standards) carry meaningful metal-content value. Plated and filled items trade at costume-jewelry prices regardless of the underlying design or brand, unless the piece has separate collector value.

Vermeil is the one hybrid worth flagging. Because vermeil requires a sterling silver base, the underlying metal has value even if the gold plating wears away. Buyers who accept jewelry for scrap will often price vermeil at the silver rate.

UK, French, and Italian Country Hallmark Systems

Beyond the US-style single-number stamp, several European countries operate independent Assay Offices that physically test and hallmark precious metal items. A full country hallmark encodes the maker, the metal, the office that tested the piece, and often the year. American buyers encounter these marks on estate pieces, imported antiques, and modern designer jewelry.

The United Kingdom (Assay Office Hallmarks)

The Hallmarking Act 1973 makes it a criminal offense to sell an unhallmarked article of gold, silver, platinum, or palladium above threshold weights within the United Kingdom. A full modern UK hallmark contains three compulsory marks (sponsor, metal fineness, and Assay Office) and one optional traditional mark (date letter).

• Sponsor’s mark: a registered set of initials identifying the maker, dealer, or importer. Registered with an Assay Office.
• Fineness mark: a three-digit number in a shaped surround. The surround shape indicates the metal: a rounded shield for gold, an oval for silver, a house-shape for platinum, and a trapezoid for palladium.
• Assay Office mark: a symbol identifying the office that tested and stamped the piece.
  • Leopard’s head = London Assay Office
  • Anchor = Birmingham Assay Office
  • Rose = Sheffield Assay Office
  • Three-towered castle = Edinburgh Assay Office
• Date letter: a single letter (case and font vary by year and by office) indicating the year of assay. Optional since 1999 but often included by tradition.

Traditional standard marks may also appear: a lion passant (walking lion) for sterling silver, a seated Britannia for 958 silver, and a crown for gold (used before 1975 in some offices). Details on current UK hallmarks are published by the Birmingham Assay Office and its sister offices.

France (Guarantee Marks)

French hallmarks use small animal or figure heads as guarantee marks (poinçons de garantie), applied by the state customs service. The system predates the modern French Republic and carries considerable historical detail; the marks a US reader is most likely to encounter are summarized below.

• Eagle head (tête d’aigle): 18 karat gold (750). In use in France since 1838.
• Owl (hibou): imported gold of unspecified fineness (post-1893).
• Horse head: 20 karat gold used in some historical periods.
• Minerva head (Minerve): silver of 925 or 800 fineness, distinguished by numerals inside the mark (1 for premier titre 950 or 925, 2 for deuxième titre 800). Used from 1838 onward.
• Boar head (hure de sanglier): silver assayed in Paris (pre-1962).
• Crab (crabe): silver assayed in the French provinces (pre-1962).
• Dog head (tête de chien): platinum, from 1912.

A French piece will typically carry both a fineness guarantee (the head or figure) and a maker’s mark (rhomboid or lozenge-shaped punch containing initials or a symbol). Detailed catalogs of French hallmarks are maintained by museums such as the Musée de l’Orfèvrerie.

Italy

Italian marks follow a compact format: the three-digit fineness (750, 925, 950), plus a maker’s mark inside a lozenge, plus a two-letter province code and a number identifying the specific manufacturer registered in that province. For example, “750 · 123 AR” indicates 18 karat gold from maker 123 registered in the province of Arezzo. The letters “OR” often precede the province code on older gold pieces; “AG” is used for silver. This registration system operates under Italian Presidential Decree 150/2002.

Other Common Marks on Estate Pieces

Older or imported items may show marks from other national systems. Common examples:

• Swiss watches: cross with “0.750” or “0.585” for gold case, often with a squirrel or Helvetia head guarantee mark.
• Russian pre-Revolutionary silver: 84, 88, or 91 zolotnik marks (equivalent to 875, 916, and 947 fine respectively).
• Scandinavian silver: three-crown mark for Sweden, dot inside a shield for Denmark, plus 830 or 925 numerals.
• Middle Eastern gold: 21 karat marks (875) common in Kuwait, UAE, and Saudi Arabia.

Maker’s Marks and Sponsor Marks

Alongside the metal mark, a serious piece of jewelry or silverware usually carries a maker’s mark: a set of registered initials, a symbol, or a combination in a distinctive punch shape. In hallmarking countries, the maker (or, for imports, the sponsor bringing the piece to market) must register the punch with the Assay Office before it can be used. In the US and other non-hallmarking countries, maker’s marks are voluntary but common on quality goods.

Identifying an unfamiliar maker’s mark takes a reference book or an online catalog. Two useful starting points: the Assay Office London maintains a public register of British sponsor marks, and specialist reference books such as Bradbury’s Book of Hallmarks cover thousands of British and Continental marks. For American silversmiths, published guides by authors including Ralph and Terry Kovel remain the standard reference.

A well-documented maker’s mark can shift a piece from scrap value to collector value. Tiffany, Cartier, Georg Jensen, and named American silversmiths command premiums well above the metal content alone.

Missing, Worn, or Suspicious Stamps: What They Tell You

The presence of a stamp is helpful but not conclusive. Its absence is a signal that requires further investigation.

When a Missing Stamp Is Normal

• American pieces made before the National Stamping Act was fully enforced (early 20th century) sometimes carry no fineness mark.
• Small items below UK hallmarking weight thresholds (1 gram for gold, 7.78 grams for silver) may not require stamping.
• Handmade or custom pieces from independent artisans occasionally skip fineness marks.
• Vintage costume jewelry designed to imitate the appearance of precious metal.
• Very worn pieces where a stamp has been polished off after decades of wear.

When a Missing Stamp Is a Red Flag

• A modern UK-sold item above the weight thresholds should carry a full Assay Office hallmark by law.
• An item advertised as “solid 18K gold” by a modern retailer with no fineness mark or manufacturer information.
• Chains and bracelets with a clasp stamped 925 or 750 while the body of the piece rings dull under an acid test (suggesting the mark is on a plated tag attached to base metal).

Signs a Stamp May Be Fake or Misapplied

• The stamp is soft-edged or blurry, as if pressed rather than struck.
• The digits do not match a recognized fineness standard (a stamp of 720 or 800 on yellow gold, for example, does not correspond to any regulated grade in the US or UK).
• Karat and country mark do not align (a US-style 18K stamp alongside a UK-style Assay Office punch that does not exist).
• Underlying metal color visible through worn spots does not match the stated karat (bright yellow through worn white gold plating).
• The piece feels notably lighter or heavier than a solid gold or silver piece of similar size should feel.

Testing Beyond the Stamp

Serious verification uses instruments, not eyes. Four testing methods are used in the trade, ranging from cheap and destructive to expensive and non-destructive.

Acid Test (Cheapest, Slightly Destructive)

A small drop of nitric acid of graded strength (10K, 14K, 18K, 22K, and silver strengths) is applied to a fresh scratch made on a testing stone. The color reaction indicates the karat. Kits cost less than $50 at jewelry supply retailers. Testing is destructive to the scratch site but not to the piece as a whole. Not accurate on plated goods once the acid penetrates the plating layer.

Electronic Conductivity Testers

Handheld electronic testers measure the electrical conductivity of the metal at the tip of a probe. Different karats and metals have different conductivity signatures. Testers cost between $100 and $400. Faster than acid, non-destructive, but calibration matters and readings on some alloys can be ambiguous.

X-Ray Fluorescence (XRF) Spectrometry

XRF is the gold standard for non-destructive verification. A handheld or benchtop XRF spectrometer beams X-rays at the piece and reads back the elemental composition, distinguishing every metal in the alloy. Reputable buyers, pawn shops, and refineries use XRF. Cost of the device runs $15,000 and up, so this is not a home test, but a $10 fee at a professional buyer or refiner is a small price for accurate identification of an unknown piece.

Specific Gravity

Precious metals have distinctive densities: gold at 19.3 g/cm3, platinum at 21.4 g/cm3, silver at 10.5 g/cm3. Weighing a piece in air and again submerged in water yields its density. This is slower and less accurate than XRF but requires only a jeweler’s scale and does not damage the piece. Best used as a corroborating check rather than as a sole method.

Professional Appraisal

For estate pieces, antique jewelry, or anything with potential collector value, a certified appraiser (Graduate Gemologist or Certified Master Appraiser) combines physical testing with hallmark identification, maker research, and market comparables. Fees typically run from $75 to $200 per piece. This is the right path for insurance appraisal, estate settlement, or any sale of significant value.

Using the Stamp When You Sell

Once you have decoded the stamp and, ideally, confirmed it with a physical test, the fineness translates directly to a scrap or resale value calculation. For solid pieces, the calculation is: weight in troy ounces multiplied by fineness (as a decimal) multiplied by the current spot price of the underlying metal. Most buyers pay a percentage of that theoretical melt value, with the discount reflecting refining costs, dealer margin, and any complications from soldered stones or unusual alloys. Comparing sealed offers from multiple licensed buyers on the same piece is the most reliable way to see the actual market price, since offer percentages vary widely by dealer.