The troy weight system is the universal system customarily used to weigh gold.
The actual gold weight (AGW) of a bullion coin or bar is the amount of fine, pure, or intrinsic gold content measured in troy ounces. It is typically used to describe gold coins. In this investment context, it is the weight and purity of the gold content that is important, NOT the gross weight of the coin or bar (which often contains other base-metals – see next section). The distinction is often a source of confusion.
The troy ounce is the standard used to weight precious metals such as gold and silver. A troy ounce (31.103 grams) is actually 10.00% heavier and therefore worth more than traditional ounce (28.349 grams).