That small card sealed with your gold bar is more than packaging. Here is what an assay card records, why buyers trust it and when opening it costs you.
Short answer: an assay card is a card sealed with a bar that records the refiner, the weight, the fineness and usually a serial number. Buyers trust a bar in its sealed card more readily, so keeping the bar sealed can make it easier to sell.
See the glossary entries for assay card, fineness and serial number.
The sealed packaging backs up the stated weight and purity, so a dealer can resell the bar without testing it. An opened or damaged card may lead a buyer to check the bar, which can mean a lower offer or a testing fee.
When you receive a bar, confirm that the serial number on the bar matches the card, that the seal is intact and that the weight and fineness match your invoice. Report any mismatch to the dealer straight away.
Keep the bar in its card in a dry place, and avoid handling the metal directly. Keep a photo of the card and note the serial number in your records, in case the card is lost.
For coins, or for bars you plan to hold for a long time, the card matters less. For anything you might sell, leave it sealed.
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