Assay
Definition
An assay is a certified test that confirms a precious-metal item’s purity and weight. The result is often recorded on an assay card that travels with the bar as proof of its content.
An assay is how a refiner or accredited lab vouches for what is actually inside a bar or coin.
Why it matters
Gold and silver are valued by purity and weight, so an independent assay turns a marketing claim into verifiable fact. A bar backed by a recognized assay is easier to sell and usually trades closer to its metal value, because the buyer does not have to retest it.
In practice
Many modern bars ship sealed in tamper-evident packaging with an assay card showing the refiner, weight, fineness, and a unique serial number. Keeping the bar in that sealed assay is generally wise; breaking the seal can prompt a buyer to request a fresh test before purchase.
Common confusion
An assay card is not a grading certificate. It states purity and weight, not condition or collectible grade. A coin can have a high purity and still show wear that affects its numismatic value.