A platinum hallmark is a fineness mark stamped or engraved on a platinum item, showing the parts per thousand of pure platinum it contains, such as 950 for 95% fine platinum. The mark's form differs by jurisdiction: the United Kingdom requires third-party assay, the United States lets the maker self-declare under federal rules, Japan certifies only on request, and China marks fineness against a national standard. This page compares all four regimes by statute or standard, then explains what Pt950, Pt900 or Pt850 means for an item's value.
What Is a Platinum Hallmark?#
A platinum hallmark states the item's platinum content in parts per thousand, written variously as Pt950, PT950, 950Pt, 950Plat or 950; all five notations denote the identical 950-parts-per-thousand fineness. According to the World Platinum Investment Council's glossary, Pt950 jewelry is 95% platinum by mass, with the remaining 5% made up of alloying metals such as ruthenium, iridium or cobalt, chosen for hardness, castability or workability rather than cost. A hallmark is not a brand name or a decorative stamp: it is the manufacturer's or assay office's declaration of metal content, the same role a fineness stamp plays on gold or silver. Buying decisions built on platinum purity start with reading that number correctly, since a Pt850 ring and a Pt950 ring of equal weight contain different amounts of platinum.
How to Read a Platinum Hallmark: Sponsor, Fineness and Assay Marks#
A UK platinum hallmark carries three compulsory marks: the sponsor's mark, the fineness mark and the assay office mark, plus an optional date letter and traditional fineness symbol. Outside the UK, most marks are voluntary or self-declared and carry only the fineness number, without this three-part structure.
The three compulsory marks are listed below.
- Sponsor's or maker's mark: identifies the manufacturer or retailer responsible for the item.
- Fineness (millesimal) mark: the numeric platinum content, such as 950, stamped in a metal-specific shield shape.
- Assay office mark: shows which UK Assay Office tested the item, a leopard's head for London, an anchor for Birmingham, a rose for Sheffield or a castle for Edinburgh.
The UK also recognizes the Convention Hallmark under the Vienna Convention on the Control of the Fineness and the Hallmarking of Precious Metal Objects, letting an item hallmarked in one member country pass as hallmarked in another, platinum and palladium included. Ruthenium and iridium, the hardening alloys most often paired with platinum, are why a Pt950/Ru piece resists scratching better than a softer, higher-fineness one, a trade-off covered in the platinum jewelry alloys comparison.
Platinum Hallmarking in the United Kingdom#
UK platinum hallmarking is a compulsory, third-party assay applied by one of four UK Assay Offices: London, Birmingham, Sheffield or Edinburgh. A UK hallmark is not something a manufacturer stamps on its own item; the piece must physically pass through one of the four offices, which independently tests and marks it before legal sale, making the UK the strictest of the four regimes compared on this page.
UK Platinum and Palladium Fineness Standards#
The UK recognizes four legal platinum fineness standards: 850, 900, 950 and 999 parts per thousand, with 850 as the legal minimum since the standard was extended in 1999. Platinum first entered UK compulsory hallmarking under the Hallmarking Act 1973's Schedule 2, Part 1, which then recognized only 950; the 1999 extension of that same schedule added 850, 900 and 999. Palladium, added to the hallmarking system decades later and covered separately as palladium jewelry, carries its own three standards under the same schedule, 500, 950 and 999, with palladium hallmarking made compulsory from 1 January 2010 for articles over 1 gram.
The table below lists the permitted UK fineness standards for all four hallmarked metals, per Schedule 2, Part 1 of the Hallmarking Act 1973.
| Metal | Permitted UK standards (parts per thousand) | Minimum legal fineness |
|---|---|---|
| Platinum | 850, 900, 950, 999 | 850 |
| Palladium | 500, 950, 999 | 500 |
| Gold | 375, 585, 750, 916.6, 990, 999 | 375 |
| Silver | 800, 925, 958.4, 999 | 800 |
UK Hallmarking Exemption Weights#
Platinum items under 0.5 grams are exempt from UK compulsory hallmarking, under Schedule 1, Part II of the Hallmarking Act 1973. That exemption weight is the lowest of the four hallmarked metals: gold is exempt below 1.0 gram and palladium below 1.0 gram, while silver's threshold, 7.78 grams, is more than fifteen times platinum's. A platinum wedding band or signet ring, at several grams, sits far above the exemption weight; only light findings, small clasps or minor decorative elements fall under 0.5 grams.
| Metal | UK hallmarking exemption weight |
|---|---|
| Gold | 1.0 g |
| Silver | 7.78 g |
| Platinum | 0.5 g |
| Palladium | 1.0 g |
Platinum Marking in the United States: FTC Rules#
Platinum marking in the United States is self-declared by the maker and policed after the fact, under the FTC Jewelry Guides (16 CFR Part 23) rather than a compulsory assay office. No US agency tests a platinum item before sale the way a UK Assay Office does; instead, 16 CFR §23.6 sets the rules a maker follows when stamping the words platinum, iridium, palladium, ruthenium, rhodium or osmium on a finished piece, and the Federal Trade Commission enforces those rules only after the fact.
US Platinum Marking Table: What Each Stamp Means#
Under 16 CFR §23.6, platinum at 950 parts per thousand or higher may be marked "Platinum" with no number, 850 to 950 must carry a numbered prefix such as "900Pt.," and under 500 pure platinum cannot be called "Platinum" unqualified. Between those two ends, an item with at least 500 parts per thousand pure platinum, where total platinum group metal content reaches 950 parts per thousand, may carry a numbered prefix naming each metal present, such as "600Pt.350Ir." A separate provision, 16 CFR §23.7, requires disclosure of any surface-layer rhodium application on a piece described as precious metal, a rule frequently missed by sellers of rhodium-plated white gold, the subject of this site's platinum-plated and rhodium-plated metals comparison.
The table below lists the US marking rule for each platinum content band, per 16 CFR §23.6 and §23.7.
| Pure platinum content | Permitted marking | Example stamp |
|---|---|---|
| 950 parts per thousand or higher | "Platinum," "Pt." or "Plat." with no number | Platinum |
| 850 to 950 | Numbered prefix stating the amount | 900Pt., 950Pt. |
| 500 to 850, fully disclosed | Each metal and amount disclosed | 585Pt., 415Co. |
| 950+ total PGM, at least 500 pure Pt | Numbered prefix per metal present | 600Pt.350Ir. |
| Under 500 pure platinum | Unqualified "Platinum" prohibited | Not applicable |
| Surface-coated (e.g., rhodium-plated) | Prohibited without disclosure of the plating | Must state "rhodium-plated" or equivalent |
Platinum Hallmarks in Japan#
Japanese platinum hallmarking is voluntary, administered by the Japan Mint, which stamps a certification mark only on items it has independently assayed. Japan recognizes four platinum fineness grades, Pt1000, Pt950, Pt900 and Pt850: Pt950 leads fine jewelry, Pt900 the volume mid-market and Pt850 accessible, chain-manufactured pieces. A stamp reading "Pt900" on a Japanese item is usually the manufacturer's own declaration, not Japan Mint certification; only the Mint's own hallmark, applied on request and most common on bridal and high-fineness pieces, constitutes independent verification, closer in principle to the UK's compulsory system than to the self-declared US one, though without the UK's legal requirement.
Platinum Marking in China: GB 11887-2012#
Chinese platinum jewelry fineness is set by GB 11887-2012, effective 1 May 2013, which permits the designations Pt950, Pt900 and Pt850. The standard, "Jewellery, Fineness of Precious Metal Alloys and Designation," was issued 5 November 2012, superseding GB/T 11887-2008. Pt950 is the dominant grade in China's bridal and fashion segments, the same grade that leads in Japan and sits mid-tier in the UK's four-step system, making 950 the one fineness figure recurring across every jurisdiction compared here. A separate number, 925, appears in some marketing copy but is not a platinum standard anywhere: 925 denotes sterling silver fineness, so an item marked 925 is silver, not a low grade of platinum.
Platinum Hallmark Standards by Country#
Platinum hallmarking differs by compulsion, standards and exemption weight across the UK, US, Japan and China. The UK alone has a compulsory, government-linked assay system; the US relies on self-declaration policed after sale; Japan's certification is voluntary; and China's marking follows a national standard with no certifying assay body. Finer distinctions within these numbers, including grades used in bullion, are covered on platinum purity grades.
| Jurisdiction | Compulsory assay? | Platinum standards | Palladium standards | Exemption weight (platinum) |
|---|---|---|---|---|
| UK | Yes, 4 Assay Offices | 850, 900, 950, 999 | 500, 950, 999 | 0.5 g |
| US | No, self-marked, FTC-policed | 950+ plain; 850-950 numbered; 500-850 qualified | Covered by the same §23.6 metals list | Not applicable |
| Japan | No, voluntary (Japan Mint) | Pt1000, Pt950, Pt900, Pt850 | Not a major grade set | Not applicable |
| China | Standard-based (GB 11887-2012) | Pt950, Pt900, Pt850 | Not covered by this standard | Not applicable |
Using a Platinum Hallmark#
A platinum hallmark tells a buyer how much of an item is platinum, not what it is worth. The number, whether 950, 900 or 850, is only a starting point; weight, condition and the day's platinum group metal prices today complete the value calculation, covered below.
What Pt950, Pt900 and Pt850 Mean for Value#
Pt950 jewelry is 95% platinum, Pt900 is 90% and Pt850 is 85%, with the remainder made up of alloying metals such as ruthenium, iridium or cobalt; 925 is not a platinum standard, it is sterling silver fineness. A 10-gram Pt950 ring contains 9.5 grams of platinum, while the same 10-gram ring at Pt850 contains 8.5 grams, a full gram less of the metal that sets scrap and resale value.
The 950 platinum grade is the most common of the three, balancing precious-metal content with workable hardness.
Jewelers choose lower-fineness alloys such as platinum 900 over higher grades for the added castability and stone-setting hardness, trading platinum content for durability.
Wear behavior differs by grade as well as by metal. Higher-fineness platinum develops a fine, reversible surface patina rather than losing metal the way plated alternatives do; does platinum tarnish explains that patina and why it differs from tarnish.
Testing Platinum Beyond the Hallmark#
A hallmark is a declared fineness, not a test result, so buyers needing independent confirmation use acid, XRF or density testing, listed below.
- Acid testing: scratches a small amount of metal onto a testing stone and applies platinum-specific acid, watching for a reaction.
- XRF testing: reads a piece's elemental composition with X-ray fluorescence, non-destructively.
- Density testing: compares weight in air against weight submerged in water, using platinum's high density relative to look-alike white metals.
Each trades accuracy against cost; how to test platinum covers all three in full.
Platinum Hallmarks FAQ#
Does platinum have a hallmark?#
Yes: platinum sold in the UK, Japan or China is hallmarked or fineness-marked, and platinum sold in the US carries a self-declared, FTC-compliant mark. The exact form differs by jurisdiction, covered in full above, but every one of the four markets requires some form of fineness disclosure before a platinum item reaches a buyer.
What is the hallmark for platinum jewelry?#
The hallmark for platinum jewelry is a numeric fineness mark such as 950, 900 or 850, showing parts per thousand of pure platinum. In the UK that number sits alongside a sponsor's mark and an assay office mark; in the US it stands alone as a self-declared stamp under 16 CFR §23.6.
Is platinum jewelry worth anything?#
A platinum hallmark's fineness figure is the starting point for its scrap value, which also depends on weight and the day's platinum price. A Pt950 ring's platinum content is worth calculating separately from its retail purchase price, since jewelry sells at a premium to metal content and buys back closer to scrap value; selling platinum jewelry for scrap walks through that calculation.
What are platinum's symbol, atomic number and CAS number?#
Platinum has the symbol Pt, atomic number 78 and CAS number 7440-06-4, with an atomic mass of 195.08 (PubChem). Those three identifiers, not the hallmark, distinguish the element itself from the alloy stamped into a piece of jewelry; the metal's full physical and chemical profile is covered on platinum (Pt), element 78.