Troy weight Troy weight Troy weight is a system of units of mass customarily used for precious metals and gemstones. One troy ounce (abbreviated "t oz" or "oz t") is equal to exactly , (or about 1.0971 oz. avoirdupois, the "avoirdupois" ounce being the most common definition of an "ounce" in the US). There are only 12 troy ounces per troy pound, rather than the 16 ounces per pound found in the more common avoirdupois system. The avoirdupois pound has 7000 grains whereas the troy pound has only 5760 grains (i.e. 12 × 480 grains). Both systems use the same grain defined
Anglo-Saxon pound Thomas Snelling writes that the division of the pound into 12 ounces was in use with the Romans, and the division of ounces into 20 pennyweights was introduced into France by Charlemagne, and then brought to England by William the Conqueror. The Latin word for "pound" is libra. The £ or ₤ is a stylised writing of the letter L, a short way of writing libra. This is similar to how a pound of mass is abbreviated "lb". Up until 1972, especially on typewriters or keyboards without a "£" symbol, it was common to write "L" or "l" instead of