A pennyweight (dwt) is a unit of mass equal to 24 grains, 1⁄20 of a troy ounce, 1⁄240 of a troy pound, approximately 0.054857 avoirdupois ounce and exactly 1.55517384 grams. It is abbreviated dwt, d standing for denarius –, and later used as the symbol of an old British penny.
17th-century Irish weight, 8 dwt
Irish gold pistole, bearing its weight (4 dwt 7 gr) (National Museum of Ireland – Decorative Arts and History)
Troy weight is a system of units of mass that originated in 15th-century Kingdom of England and is primarily used in the precious metals industry. The troy weight units are the grain, the pennyweight, the troy ounce, and the troy pound. The troy grain is equal to the grain unit of the avoirdupois system, but the troy ounce is heavier than the avoirdupois ounce, and the troy pound is lighter than the avoirdupois pound. One troy ounce equals exactly 31.1034768 grams.
Troy ounce is a traditional unit of gold weight.
One-troy-ounce (480 gr; 31 g) samples of germanium, iron, aluminium, rhenium and osmium
A Good Delivery silver bar weighing 1,000 troy ounces (83 troy pounds; 31 kg)
The standard British troy pound manufactured in 1758; it bears the abbreviation ℔ ("pound") and the letter "T" for troy.
