It's a weight measurement used for gold, silver, and precious metals.
( The regular ounce measurement we use when we buy sugar, for example, is called an "avoirdupoids"ounce. 16 regular ounces equals a pound)
A troy ounce is more than the typical ounce found at the grocery store.
One troy ounce (oz t) is equal to 31.1034768 grams.
It takes 12 troy ounces to make a troy pound .Although not sure, the troy weight probably gets its name from the French town of Troyes in France.