Assay / Assay Certificate
Also: assay card, bar certificate, certificate of assay, test certificate
Issued by an accredited testing body, an assay certificate is an authenticity document that binds together confirmation of a precious-metal bar's fineness, weight and identity.
An assay certificate — sometimes labelled a certificate of assay, or just an assay card — is a document put out either by an independent, accredited testing body or by the manufacturer itself, and tied permanently to a particular precious-metal bar. Its purpose is to certify, in a binding way, that the bar has exactly the properties claimed for it: above all its fineness, together with gross weight, fine weight and serial number. Short of a full chemical analysis, no other tool gives a buyer as much assurance of authenticity.
How the certificate comes about
Once a bar has been cast or struck, the refinery — or a laboratory acting on its behalf — draws a material sample and runs it through analysis. The usual techniques are:
- Fire assay (cupellation): a time-tested wet-chemical procedure, treated as the reference standard for gold and silver.
- X-ray fluorescence analysis (XRF): contactless spectral measurement, quick and non-destructive.
- Flame atomic absorption (FAAS): a highly precise route for reading trace elements and alloy constituents.
Whatever the outcome, it is written onto the certificate and tied to an individual serial number that is either engraved or stamped into the bar.
What the certificate contains
| 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 inside a blister
By far the most common method of fusing certificate to bar for good is the blister (also called assay card packaging): bar and certificate are sealed as one inside a clear plastic pack. For as long as that blister stays sealed and intact, the bar it holds ranks as certified and untouched. Break or damage the blister and the dealer buy-back price usually drops, because there is no longer an airtight way to prove that this bar and this certificate belong together.
Assay certificate set against LBMA Good Delivery
The LBMA Good Delivery label works differently: rather than certifying each bar one by one, it accredits the manufacturer and its production process. A Good Delivery bar (the 400-troy-ounce standard bar of institutional trading) does bear stamps giving a serial number and fineness, yet it travels without an enclosed assay card. As a physical accompanying document, the assay certificate matters most for the small bars (1 g up to 1 kg) sold in the retail market.
What it does for you when buying and reselling
At the point of buying gold, the assay certificate delivers three concrete benefits:
- On-the-spot authenticity control with no testing gear of your own — the serial number engraved on the bar has to line up with the one on the certificate.
- Stronger resale terms — dealers will generally take back a certified bar still in its original blister with no re-testing surcharge, whereas uncertified material tends to attract a deduction from the melt value.
- A paper trail for inheritances and insurance — the certificate stands as proof of the bar's identity and worth.
Regardless of the certificate, you can work out a bar's melt value whenever you like, drawing on the current gold price and the stated fine weight.
In brief
By tying a specific bar — through its serial number — to an independent test of fineness and weight, an assay certificate builds trust on the back of verifiable provenance. When you buy small bars, leaving the blister sealed keeps its documentation value fully intact. For any tax or investment questions around reselling, seek out a professional adviser.