Assay / Assay Certificate
Also: Assay Card, Bar certificate, Certificate of Assay, Test certificate
An assay certificate is an authenticity document issued by an accredited testing body that bindingly confirms the fineness, weight and identity of a precious-metal bar.
An assay certificate (in full a Certificate of Assay, or Assay Card for short) is a document issued by an independent, accredited testing body or by the manufacturer itself and permanently assigned to a precious-metal bar. It bindingly certifies that the bar in question possesses the stated properties - in particular fineness, gross weight, fine weight and serial number. For buyers the certificate is the most important instrument of authenticity control short of a full chemical analysis.
How an assay certificate is created
After a bar has been cast or minted, the refinery or a commissioned laboratory takes a material sample and analyses it. Common methods are:
- Fire assay (cupellation): the classic wet-chemical method, regarded as the reference technique for gold and silver.
- X-ray fluorescence analysis (XRF): a contactless spectral analysis, fast and non-destructive.
- Flame atomic absorption (FAAS): a high-precision method for trace elements and alloy constituents.
The result is recorded on the certificate and assigned to an individual serial number that is engraved or stamped on the bar.
Structure of an assay certificate
| Mandatory entry | Example |
|---|---|
| Manufacturer / testing body | PAMP Suisse, Heraeus, Valcambi |
| Bar number (serial number) | 00412857 |
| Metal | Gold (Au) |
| Gross weight | 31.103 g (1 troy ounce) |
| Fineness | 999.9/1000 |
| Fine weight | 31.100 g |
| Test date | 2026-07-25 |
| Stamp / signature of the testing body | Embossing or hologram |
Certified bars in the blister pack
The most common way to bind an assay certificate permanently to a bar is the so-called blister (also assay card packaging): bar and certificate are sealed together in a transparent plastic pack. As long as the blister is unopened and undamaged, the enclosed bar is considered certified and untouched. A broken or damaged blister generally lowers the dealer buy-back price, because the link between bar and certificate can no longer be proven beyond doubt.
Assay certificate vs. LBMA Good Delivery
The LBMA Good Delivery label is not an individual certificate for every bar but an accreditation for the manufacturer and its production process. A Good Delivery bar (a 400-troy-ounce standard bar for institutional trading) does carry stamps with serial number and fineness, but no accompanying assay card. The assay certificate as a physical accompanying document is primarily relevant for small bars (1 g to 1 kg) in the retail segment.
Practical benefit when buying and reselling
When buying gold the assay certificate offers three concrete advantages:
- Immediate authenticity check without your own testing equipment - the serial number on the bar must match the certificate.
- Better resale conditions - dealers usually accept certified bars in the original blister without a surcharge for a fresh test; for uncertified material a discount from the melt value is often applied.
- Documentation for estates and insurance - the certificate serves as proof of the bar's identity and value.
You can calculate the melt value of a bar independently of the certificate at any time, based on the current gold price and the stated fine weight.
In brief
An assay certificate builds trust through provable origin: it links a specific bar, via its serial number, to an independent test of fineness and weight. When buying small bars the blister should always remain unopened in order to preserve the full documentary value. Any tax or investment questions about reselling should be clarified with a professional adviser.