Silver purity is expressed as fineness — the proportion of pure silver by mass, measured in parts per thousand.
The two standards you’ll encounter most often:
- .999 fine (“three nines”) — 99.9% pure silver. This is the standard for American Silver Eagles, most silver bars, and the majority of silver bullion products worldwide.
- .9999 fine (“four nines”) — 99.99% pure silver. The standard for Canadian Silver Maple Leafs and a handful of other premium products.
The practical difference in metal content between .999 and .9999 is one part per thousand — about 0.031 grams per troy ounce. For bullion purposes this is economically negligible. The .9999 standard exists primarily for reasons of precision manufacturing and carries a slight prestige premium in some markets.
Sterling silver (used in jewelry and silverware) is .925 fine — 92.5% silver, 7.5% copper for hardness. Sterling is not bullion. It trades at a discount to pure silver because of the alloy content and the cost of assaying and refining it back to .999+.
Older silver coins (pre-1965 U.S. dimes, quarters, half-dollars) are typically .900 fine — 90% silver, 10% copper. These are often called “junk silver” and trade close to their melt value.
When buying bullion, stick to .999 or higher for clean resale.
Sources
For detailed purity specs and head-to-head comparisons across major government coins, see Best Coins for Stackers.