When a bar arrives sealed in a card with a serial number, or a coin comes in a sealed mint tube, that packaging is part of the product. Opening it is the most common avoidable mistake bullion owners make.
What an assay card is
An assay is a test confirming the composition and purity of a metal. An assay card is the sealed package a minted bar arrives in, carrying the refiner's mark, the weight, the fineness, and usually a unique serial number matching the number stamped on the bar itself.
The card is tamper evident. Once opened, it cannot be resealed convincingly, and that is the point. An intact card is evidence the bar has been undisturbed since it left the refinery.
Why serial numbers matter
A serial number ties a specific bar to a specific assay. It lets a dealer confirm the bar in front of them is the bar the card describes, and it gives you a way to record exactly what you hold.
For insurance purposes a serial number is far more useful than a general description. For a claim, being able to specify a serial number is meaningfully different from saying you held a bar of a certain size.
What happens when you open it
Nothing dramatic, but the verification chain breaks.
A sealed bar can be priced quickly, because the packaging supports the claim about what it is. An unpackaged bar of the same weight and purity may need testing before a dealer will quote confidently, and that testing takes time. On smaller bars in particular, the effort can be disproportionate to the value, which some dealers reflect in what they offer.
The gold or silver is unchanged. What changes is how easily someone else can be sure of that.
Mint tubes
Sovereign coins are issued in mint tubes, commonly 20 or 25 coins depending on the mint. A sealed tube serves a similar function to an assay card, and it also protects the coins physically, keeping them from rubbing against each other and limiting air contact.
Buying a full tube is generally cheaper per coin than buying singles. If you have no reason to open it, leave it sealed.
Practical rules
Leave sealed items sealed. Curiosity is the usual reason people open them, and it costs more than it gives.
Do not throw packaging away. Even if a card has been opened, keeping it preserves the serial number and the assay information.
Record serial numbers separately. Keep a list somewhere other than with the metal. If the bullion is lost or stolen, the list needs to survive independently.
Photograph what you hold. Images showing serial numbers and packaging are useful for insurance and take a few minutes.
Keep invoices. Purchase documentation establishes when and where an item was acquired, which matters more than people expect at resale.
What about coins in capsules
Individual coin capsules are protective rather than evidentiary. They keep fingerprints and air off the coin but carry no verification information, so opening one costs nothing beyond exposing the coin to handling. That is different from an assay card or a sealed tube.
Our storage guide covers handling in more detail.
Frequently asked questions
What is an assay card?
Tamper evident sealed packaging carrying the refiner's mark, weight, fineness and usually a serial number matching the bar inside.
Should I open the assay packaging on my bar?
No. An intact seal supports verification and makes resale simpler and quicker.
Does opening packaging reduce the value?
The metal content is unchanged. What changes is how easily a dealer can verify it, which can affect how quickly and confidently they quote.
Why do bars have serial numbers?
To tie a specific bar to a specific assay, and to give owners a precise way to record and insure what they hold.
Should I open a sealed mint tube?
Only if you need to. Sealed tubes protect condition and keep the coins together.
Browse sealed products
We stock minted bars in assay packaging and coins in mint tubes. See the range or visit the showroom at 124 Peterborough Street, Christchurch.