Troy weight Wikipedia

Troy weight is a system of units of mass that originated in 15thcentury England, and is primarily used today in the precious metals industry. Its units are the grain, pennyweight (24 grains), troy ounce (20 pennyweights), and troy pound (12 troy ounces). The grain is the same grain used in the more common avoirdupois contrast, the troy ounce is heavier than the avoirdupois ounce ...