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
Silver center cent of the new nation's coinage should be approximately equal to its face value. Some merchants would refuse to accept coins that did not meet this standard. For most denominations, bullion parity was achieved by producing the coins in a gold or silver alloy. However, the Coinage Act of 1792 specified that the cent was to consist of 11 pennyweight (264 grains or 17.1 g) of pure copper. Such a weight, needed to maintain intrinsic value, would have been too heavy for practical everyday use. U.S. Secretary of State Thomas Jefferson suggested an alternative: a coin made of an alloy that