What are Troy Pounds?
A troy pound is about 373.24 grams, which makes it lighter than the avoirdupois pound of 453.59 grams. It was the pound of the precious metals trade, though gold and silver are now quoted per troy ounce.
One troy pound is equivalent to 12 troy ounces, which is lighter than the avoirdupois pound commonly used in everyday measurements. The troy pound is often denoted by the symbol "lb t" to distinguish it from the avoirdupois pound.
What are pennyweights?
Pennyweights are a unit of measurement commonly used in the jewelry industry to measure the weight of precious metals such as gold and silver.
A pennyweight is 1/20th of a troy ounce, which is 1.55517 grams. Jewelers still use it for small amounts of gold and silver.
To get grams from pennyweights multiply by 1.555 – 10 pennyweights is about 15.55g. The abbreviation dwt comes from d for denarius, the old penny.