Pennyweight is derived from the price for a hundred nails in 15th century England: the larger the nail, the higher the cost per hundred. The pennyweight also bears no relation to the weight of the American "penny" (1 cent) coin, which weighs 2.5 g (for those minted after 1982). Pennyweight A pennyweight (abbreviated dwt, from denarius weight) is a unit of mass that is equal to 24 grains, of a troy ounce, of a troy pound, approximately 0.054857 avoirdupois ounce and exactly 1.55517384 grams. In the Middle Ages, a British penny's weight was literally, as well as monetarily, of an ounce
Penny (English coin) modern grains (1.3 to 1.5 g). It was standardized to 32 Tower grains, 1/240th of a Tower pound (approx. 350 g). The alloy was set to sterling silver of 925/1000 in 1158 under King Henry II. The weight standard was changed to the Troy pound (373.242 g) in 1527 under Henry VIII, i.e. a pennyweight became about 1.555 grams. As the purity and weight of the coin was critical, the name of the moneyer who manufactured the coin, and at which mint, often appeared on the reverse side of the coin. From the time of King Offa, the penny was