Guides
London hallmarks: what they mean on Amada jewellery
Quick answer
London hallmarks — metal proof, not diamond grade
A London hallmark is not a brand logo. It is not a diamond grade. It is an independent Assay Office mark struck on gold, silver, platinum or palladium after the metal is tested against a legal fineness standard.
That is how you know the metal matches what you were sold. We finish pieces in Hatton Garden and hallmark them in London before they ship. Not a slogan. A production step.
Precious metal can be alloyed, plated, or misdescribed. The Assay Office samples, tests, and marks what meets the standard. Metal integrity — not marketing.
How to buy with hallmarks in mind
- Match metal to daily life. Platinum and 18 carat gold are common for engagement wear. We will talk trade-offs without mystique.
- Ask where hallmarking happens. “Hallmarked” with no office is weaker than naming Assay Office London.
- Split metal trust from stone trust. Confirm London hallmarking on the mount. For the diamond: if it is sold as certified, verify the report number. Not every ring carries a full lab report — fashion pieces and accent-only designs often do not. Read the listing.
- Policies are separate. Hallmarking does not replace returns, insured delivery, or the manufacturing warranty.
Cannot show where the piece was assayed? Waves away the difference between a maker’s stamp and an Assay Office mark? Slow down. Basic Hatton Garden questions.
Hallmark vs certificate
Both sound like “official stamps.” They answer different questions.
| Mark type | What it tells you | What it does not |
|---|---|---|
| Fineness / metal mark | Legal precious-metal standard of the article assayed | Whether the diamond is lab-grown or natural |
| Assay Office (London) | Which office tested and marked the metal | Where the diamond was grown or mined |
| Sponsor’s mark | Who submitted the piece for assay | Retail price, warranty, or returns |
| Diamond certificate (IGI / GIA) | Independent grading of the stone when certified | Metal fineness of the mount |
- Hallmark → Is this precious metal what it claims to be?
- Certificate → What are the graded characteristics of this diamond?
When a product lists IGI or GIA, that is the stone. “London hallmarked” is the metal. Open both when both apply — do not invent a certificate if the listing does not claim one.
What you will see on a London hallmark
Traditional UK hallmarking stacks several marks. Learn four ideas, not a museum lecture:
- Sponsor’s mark — who submitted the article for hallmarking.
- Metal and fineness — e.g. 750 for 18 carat gold, 950 for platinum.
- Assay Office — for London, historically the leopard’s head.
- Date letter — year cycle on many traditional marks.
You do not need every symbol memorised. You need this: the Assay Office is testing metal under UK law — not restating cut, colour, or clarity.
Common engagement and wedding fineness: 375 / 585 (9ct / 14ct where used), 750 (18ct), 950 (platinum). The number is content, not a beauty ranking. Choose metal for colour, weight, durability, budget — then confirm the mark matches what you were sold.
Why London and Hatton Garden
Hatton Garden is not a caption for us. It is where we manufacture and finish — showroom and workshop in the quarter. London assay is part of selling honestly in the UK.
Make → finish → assay → ship. That is why lead times stay practical. Most made-to-order finishes in about 2–3 weeks, then marked before dispatch. Ready-to-ship follows the same metal standard — already through the queue.
Visit 34 Greville Street or the workshop and ask to see marks on a finished band. In person or on video beats any diagram. You will learn the difference between a retail stamp and a true hallmark fast.
Common mistakes
- Thinking the hallmark grades the diamond. It does not.
- Ignoring fineness when comparing “gold” that is not the same standard.
- Assuming every stamp inside a band is a hallmark. Maker’s marks, size marks, retail codes ≠ Assay Office.
- Skipping certification checks when a listing claims a certified centre. Sold as certified? Verify. Not? Do not invent one — and never treat the hallmark as a diamond grade.
- Treating “hallmarked” as returns or warranty. Different contracts.
How Amada does this
Hatton Garden manufacturer-retailer. Third-generation jewellers. Twenty years online. Trade stock plus retail so sizes and specs actually exist. Made and finished in our workshop, then hallmarked in London before ship.
“London hallmarked” on our trust bar is a production step — not a photoshoot slogan. Same path keeps availability high and most custom work in weeks, not a vague season.
Still choosing a shape? Browse engagement rings and ready to ship, or book with the team. Trade-side story: BuyFineDiamonds and their diamond guide — same workshop family, same metal standards.
Related: lab-grown vs natural, engagement ring buying guide, diamond certification, why lab diamond, our story. Soft look-finder: Amada Atelier.
Policies beside the hallmark
Summaries only. Full terms on the linked pages. Nothing here extends rights beyond applicable UK consumer law.