Troy weight was customarily used for precious metals, black powder and gemstones.
From the en.wikipedia.org
Like other precious metals, gold is measured by troy weight and by grams.
From the en.wikipedia.org
English troy weights were apparently derived from the nearly identical troy weight system of Bremen.
From the en.wikipedia.org
The origin of the troy weight system is unknown.
From the en.wikipedia.org
Troy weight, avoirdupois weight, and apothecaries'weight are all built from the same basic unit, the grain, which is the same in all three systems.
From the en.wikipedia.org
Troy weight probably takes its name from the French market town of Troyes in France where English merchants traded at least as early as the early 9th century.
From the en.wikipedia.org
For example, in apothecary and troy weight, the pound and ounce are the same, but are different from the pound and ounce in avoirdupois in terms of their relationships to grains and to each other.
From the en.wikipedia.org
It was derived from another silver coin, the sceat, of 20 troy grains weight, which was in general circulation in Europe during the Middle Ages.
From the en.wikipedia.org
The English silver penny was derived from another silver coin, the sceat, of 20 troy grains weight, which was in general circulation in Europe during the Middle Ages.