Purity, also called fineness, states how much of a piece is precious metal. A .999 fine silver coin is 99.9 percent silver. The modern licensed standard is .999, and some issues go to .9999.

Higher purity is not automatically more collectible. The difference between .999 and .9999 is negligible to the eye and to the value of a licensed issue, where the mintage and the grade carry far more weight. Purity matters most for confirming a piece is what it claims to be.