Carat (mass) quarters" of 15 grains troy each. Likewise, the ounce troy was divisible into 24 "ounce carats" of 20 grains troy each; the ounce carat was divisible into four "ounce grains" of 5 grains troy each; and the ounce grain was divisible into four "ounce quarters" of grains troy each. The "solidus" was also a Roman weight unit. There is literary evidence that the weight of 72 coins of the type called "solidus" was exactly 1 Roman pound, and that the weight of 1 "solidus" was 24 "siliquae". The weight of a Roman pound is generally believed to have been 327.45
Troy weight was based on the tower pound, which is of a troy pound.) The "d" in "dwt" stands for "denarius", the ancient Roman coin that equates loosely to a penny. The symbol "d" for penny can be recognized in the notation for British pre-decimal pennies, in which pounds, shillings, and pence were indicated using the symbols "£", "s", and "d", respectively. For example, "£6 11s 8d" indicated six pounds, eleven shillings, and eight pence. Mint weights, also known as "moneyers' weights" were legalised by Act of Parliament dated 17 July 1649 entitled "An Act touching the monies and coins of England".