Gold Fineness Stamps: What Do the Numbers Inside Your Ring Mean?
Gold fineness stamps are the small numbers punched inside a ring's band that declare exactly how much pure gold the piece contains. Whether the stamp reads 375, 750, or 916, each number is a guarantee — tested and verified by an independent assay office before the ring left the workshop. This guide explains what each fineness number means, how the British stamping system evolved through four key legislative changes, and how to use fineness marks to date antique rings.
What Does the Fineness Number Inside a Ring Mean?
The fineness number expresses gold purity in parts per thousand. A stamp reading 750 means the ring contains 750 parts gold out of every 1,000 — equivalent to 75% pure gold, or 18 carat. The mathematical relationship is straightforward: divide the carat value by 24 and multiply by 1,000.
This millesimal system replaced the older carat-based stamps in Britain from 1975, but the principle is the same. Whether a ring is stamped "18" (pre-1975) or "750" (post-1975), both confirm the same gold content. The table below shows every fineness value used in British hallmarking and its carat equivalent.
| Millesimal Fineness | Carat | Gold Content | British Legal Standard |
|---|---|---|---|
| 999 | 24ct | 99.9% | Legal but not used for rings |
| 916 | 22ct | 91.6% | Legal since the earliest hallmarking statutes |
| 750 | 18ct | 75.0% | Legal since 1798 (reintroduced) |
| 625 | 15ct | 62.5% | 1854–1932 only |
| 585 | 14ct | 58.5% | Legal since 1932 (replaced 15ct and 12ct) |
| 500 | 12ct | 50.0% | 1854–1932 only |
| 375 | 9ct | 37.5% | Legal since 1854 |
How Did Gold Fineness Stamps Change Through British History?
British gold fineness marking evolved through four distinct legislative phases, each leaving its own characteristic stamp on the rings produced during that period. Identifying which phase a stamp belongs to is one of the most reliable methods for dating antique jewellery, because certain fineness values were legal only during specific decades.
The system begins with the Goldsmiths' Company and the earliest hallmarking statutes, which permitted only high-purity gold. Over four centuries, Parliament and the assay offices gradually expanded the range of legal fineness standards in response to changing demands — from the needs of Georgian watchmakers to the mass market of the Industrial Revolution.
Before 1854: Only 22ct and 18ct
For most of British hallmarking history, only two gold purities were legal. The 22ct standard was the sole permitted fineness from 1575 until 1798, when 18ct was reintroduced as an additional standard at the request of watchmakers who needed a harder metal. The 18ct standard had existed before 1575 but was removed to simplify enforcement.
The marks from this period are distinctive. 22ct gold carried the lion passant (in England) alongside the assay office mark and maker's mark. From 1816, a "sun in splendour" symbol was struck on 22ct pieces as an additional identifier. The 18ct standard received a crown and the figure 18, stamped into the band alongside the other hallmark components.
1854–1932: The Expansion to Five Standards
The Gold and Silver Wares Act 1854 transformed British jewellery production by introducing three new gold standards: 15ct, 12ct, and 9ct. This legislation responded to demand for more affordable and durable gold — lower-carat alloys suited the mass production of jewellery for the expanding Victorian middle class, and watchmakers needed robust metals for cases subjected to daily wear.
The new fineness marks took a different form from the established 22ct and 18ct stamps. Instead of symbolic marks, the lower-carat standards were stamped with their carat number and decimal equivalent: 15/.625 for 15ct, 12/.5 for 12ct, and 9/.375 for 9ct. These items did not initially receive the crown mark that distinguished the higher purities.
Any ring bearing a 15ct or 12ct stamp was made between 1854 and 1932 — a seventy-eight-year window that makes these fineness marks particularly useful for dating. Discover our 15ct gold rings — each one made during this specific period of British goldsmithing. For the full history of this discontinued standard, read our guide to why some antique pieces are 15ct gold.
1932–1975: Rationalisation to Four Standards
In 1932, an Order in Council (S.R. & O. 1932/654) abolished the 15ct and 12ct standards and replaced them with a single 14ct standard. This rationalisation aligned British practice with continental European norms, where 14ct (585 fineness) was already the established mid-range standard. The change was administrative rather than parliamentary — enacted by Order in Council rather than a full Act.
After 1932, British gold was hallmarked in four purities: 22ct, 18ct, 14ct, and 9ct. The stamps continued to use the carat system with the familiar crown mark on 22ct and 18ct pieces. The 14ct standard saw limited adoption in Britain, where buyers and jewellers continued to favour the established 9ct and 18ct purities.
1975 Onwards: Millesimal Fineness
The Hallmarking Act 1973, which took effect in 1975, replaced the carat system with millesimal fineness numbers across all precious metals. Under this system, gold purity is expressed in parts per thousand: 375 for 9ct, 585 for 14ct, 750 for 18ct, and 916 for 22ct. These three-digit numbers are stamped inside the band alongside the other hallmark components.
The switch to millesimal fineness was part of a broader modernisation that also simplified the marking system and aligned British practice with international standards. The numbers are unambiguous — a stamp reading 750 means precisely 75.0% gold, regardless of which country's hallmarking system the reader is familiar with.
| Period | 22ct Mark | 18ct Mark | 15ct Mark | 9ct Mark |
|---|---|---|---|---|
| Pre-1854 | Lion passant + crown | Crown + 18 | Not legal | Not legal |
| 1854–1932 | Crown + 22 | Crown + 18 | 15/.625 | 9/.375 |
| 1932–1975 | Crown + 22 | Crown + 18 | Abolished | Crown + 9/.375 |
| 1975 onwards | 916 | 750 | — | 375 |
How Can Fineness Stamps Help Date an Antique Ring?
Fineness stamps narrow the possible date range of an antique ring more precisely than almost any other single hallmark component. Certain fineness values existed only during specific periods of British law, making them conclusive dating evidence that cannot be faked by style or construction alone.
A ring stamped 15ct or 12ct was made between 1854 and 1932 — no earlier and no later. A ring stamped 14ct was made after 1932, when 14ct replaced the discontinued 15ct and 12ct standards. A ring with millesimal fineness numbers (375, 585, 750, 916) was hallmarked after 1975. And a ring marked only with 22ct or 18ct, using the old crown-and-number format, predates the 1975 changeover.
Combined with the date letter (a single letter that identifies the year of assay) and the assay office mark, a fineness stamp can help pin a ring's production to a specific decade or even a specific year. Use the Hallmark Finder to decode the full set of marks on any ring in your collection.
| Fineness Stamp | Date Range | Notes |
|---|---|---|
| 15ct or 15/.625 | 1854–1932 | British-only standard, discontinued |
| 12ct or 12/.5 | 1854–1932 | British-only standard, discontinued |
| 14ct or 585 | 1932 onwards | Replaced 15ct and 12ct |
| Millesimal (375, 750, 916) | 1975 onwards | Current system |
| Crown + 18 (no millesimal) | 1798–1975 | Pre-millesimal 18ct mark |
| Sun in splendour (on 22ct) | 1816 onwards | Additional 22ct identifier |
How Do Assay Offices Test Gold Fineness?
Every fineness stamp represents an independent test carried out by one of the four remaining UK assay offices — London (the Goldsmiths' Company), Birmingham, Sheffield, and Edinburgh. The ring is not stamped by the maker; the assay office applies its marks only after verifying the gold content meets the declared standard.
Modern assay offices primarily use X-ray fluorescence spectroscopy (XRF), a non-destructive technique that determines gold content in under 30 seconds. XRF works by directing a primary X-ray beam at the metal surface and measuring the fluorescent X-rays emitted in response — each element produces a characteristic energy signature, allowing the instrument to identify the precise composition of the alloy. The Sheffield Assay Office notes that XRF can detect over 90% of elements in the periodic table and measure up to 24 elements simultaneously.
Before XRF became standard around 2004, assay offices used fire assay — a destructive process requiring a small sample of metal to be physically removed from the piece. Fire assay (also called cupellation) is a process described by the London Assay Office as over 2,000 years old. It involves inquarting the gold alloy with silver and lead, then heating the mixture in a porous cupel at 1,100°C. The base metals are absorbed into the cupel, leaving pure gold behind to be weighed. Fire assay remains the legal referee method for disputes, though routine testing now relies entirely on XRF.
| Method | Era | Destructive? | Speed |
|---|---|---|---|
| Fire assay (cupellation) | Pre-2004 (and referee) | Yes — requires a metal sample | Hours |
| XRF spectroscopy | 2004 onwards | No — entirely non-destructive | Under 30 seconds |
What Happens if Gold Does Not Meet Its Declared Fineness?
The Hallmarking Act 1973 makes it a criminal offence to describe an unhallmarked article as being made of gold, silver, platinum, or palladium in the course of trade. Enforcement falls to local Trading Standards officers, who have the power to inspect premises and seize non-compliant items.
Active enforcement continues. In March 2025, London Trading Standards seized over £250,000 worth of unhallmarked jewellery, including a single Camden Market operation that recovered more than 800 items valued at approximately £200,000. The Goldsmiths' Company supports these operations through its Touchstone Award, which recognises Trading Standards teams for their work combating hallmarking fraud.
The British Hallmarking Council, an executive non-departmental public body constituted under Section 13 of the Hallmarking Act 1973, oversees the activities of all four UK assay offices. It operates under the sponsorship of the Department for Business and Trade and ensures that the hallmarking system maintains its integrity as an independent guarantee of precious metal purity.
How Does British Gold Fineness Compare to International Standards?
The UK was a founding signatory of the International Convention on the Control and Marking of Articles of Precious Metals, signed in Vienna on 15 November 1972. The Convention established a system of mutual recognition: articles bearing the Common Control Mark (CCM) can enter any contracting state's territory without additional testing or marking, provided they meet legal fineness requirements.
The Convention recognises gold at five millesimal fineness levels: 375, 585, 750, 916, and 999. Of these, 750 (18ct) and 585 (14ct) are universal legal standards accepted across all contracting states. The Convention's millesimal system directly influenced the UK's adoption of the same numbering in 1975, replacing the traditional carat stamps with a universal numerical language for gold purity.
Not all countries require hallmarking. The United States, for example, has no compulsory hallmarking system — gold is marked with its karat value (10K, 14K, 18K) by the manufacturer, without independent assay office verification. Imported rings sold in the UK must be hallmarked by a UK assay office before they can legally be described as gold. The London Assay Office handles import hallmarking for pieces entering the British market.
Which Gold Fineness Should You Choose?
The right fineness depends on how the ring will be worn, your aesthetic preferences, and whether historical character matters to you. Each fineness level brings a distinct combination of colour, hardness, and era-specific provenance that suits different purposes.
For daily wear, 18ct gold offers the best balance of durability, colour richness, and chemical resistance. The alloy is hard enough to hold gemstone settings securely and resilient enough to absorb impacts without cracking. Explore our collection of 18ct gold rings to see pieces spanning from the Georgian period through the twentieth century.
For plain wedding bands, 22ct gold remains the traditional British choice. Its softness is acceptable in a simple band without stone settings, and the deep buttery colour carries the weight of a convention that predates the nineteenth century. Browse our 9ct gold rings for more affordable options that prioritise durability over gold content.
For collectors, rings in 15ct gold hold particular value because the fineness stamp itself serves as dating evidence — every 15ct ring was made between 1854 and 1932. The same applies to 12ct pieces. These discontinued standards represent a finite, historically bounded category that can never grow. For a comprehensive guide to how gold purity affects an antique ring's colour, durability, and value, see our article on gold purity in antique jewellery.
For a complete guide to reading hallmarks on antique rings, including the maker's mark, assay office mark, and date letter, see our step-by-step walkthrough. To understand how hallmarks relate to specific eras of jewellery production, explore our guide to Victorian rings — the era that saw the most dramatic expansion of legal gold standards. Explore our complete guide to hallmarks and authentication for the full collection of hallmarking guides.
Frequently Asked Questions
What does 375 stamped inside a ring mean?
A stamp reading 375 indicates the ring is 9ct gold — containing 375 parts pure gold per 1,000, or 37.5% gold. The remaining 62.5% consists of alloy metals, typically copper and silver, which give the metal greater hardness and durability. The 375 stamp has been the standard way to mark 9ct gold in Britain since 1975, when millesimal fineness replaced the older carat-based stamps.
Is 375 gold real gold?
375 gold is genuine gold containing 37.5% pure gold. It has been a legally recognised standard in Britain since the Gold and Silver Wares Act 1854. When hallmarked by a UK assay office, a 375-stamped ring carries the same independent guarantee of purity as any higher-fineness piece — the stamp confirms it was tested and meets the declared standard.
What is the difference between carat and millesimal fineness?
Carat expresses gold purity as parts out of 24 (18ct = 18/24 = 75% gold), while millesimal fineness expresses it in parts per thousand (750 = 75% gold). Both systems describe the same physical property — the proportion of pure gold in the alloy. Britain used carat stamps until 1975, when the Hallmarking Act 1973 introduced millesimal fineness numbers. A ring stamped "18" and one stamped "750" contain identical gold content.
How can I tell how old my gold ring is from its fineness stamp?
Certain fineness stamps narrow the date range significantly. A 15ct or 12ct stamp means the ring was made between 1854 and 1932. A 14ct stamp means it was made after 1932. Millesimal numbers (375, 585, 750, 916) indicate hallmarking after 1975. Combining the fineness stamp with the date letter and assay office mark can often pin a ring to a specific year.
Why do some antique rings have no fineness stamp?
Rings below the minimum weight threshold were exempt from compulsory hallmarking in Britain. Before 1975, gold items under approximately one gram did not require hallmarks. Imported pieces may carry different marking systems, and some very early pieces predate systematic hallmarking. Use the Hallmark Finder to check what marks should be present on a ring of a given age and origin.
Do assay offices still use fire assay to test gold?
Fire assay (cupellation) remains the legal referee method for gold testing in the UK, but routine assaying now uses X-ray fluorescence spectroscopy (XRF). XRF provides non-destructive analysis in under 30 seconds, replacing the older process that required physically removing a sample of metal from the piece. The shift to XRF became standard across UK assay offices around 2004.
Related Reading
- Gold in Antique Jewellery: Purity, Colours & What to Choose — a comprehensive guide to how gold carat affects colour, durability, and value in antique rings
- How to Read a Hallmark: Step by Step — decode the full set of marks inside your ring, including maker's mark, assay office, and date letter
- Victorian Rings: Romance, Mourning & Empire — the era that saw the most dramatic expansion of British gold standards
- Explore our complete guide to hallmarks and authentication — the Hallmarks pillar page