Dollar silver. The US Mint continues to make silver $1-denomination coins, but these are not intended for general circulation. The quantity of silver chosen in 1792 to correspond to one dollar, namely, 371.25 grains of pure silver, is very close to the geometric mean of one troy pound and one pennyweight. In what follows, "dollar" will be used as a unit of mass. A troy pound being 5760 grains and a pennyweight being 240 times smaller, or 24 grains, the geometric mean is, to the nearest hundredth, 371.81 grains. This means that the ratio of a pound to a dollar (15.52)
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".