Pennyweight 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 and of a pound of sterling silver. At that time, the pound in use was the Tower pound, equal to 7,680 Tower grains (also known as wheat grains). The medieval English pennyweight was thus equal to 32 Tower grains. When Troy weights replaced Tower weights in 1527, the
Great Recoinage of 1816 shillings weighing 87.2727 grains (or 5.655 grams), half-crowns of 218.1818 grains (14.138 grams) and crowns of 436.3636 grains (28.276 grams). Over the many reigns until decimalisation other denominations came and went, such as the threepence, sixpence, florin, and double florin, always weighing exactly one troy pound per 66 shillings (irrespective of fineness, which was reduced to 50% in 1920, and to 0% in 1947). This made 5 sterling silver shillings (which is 1 crown), about the weight of .9091 troy ounce of sterling silver. Great Recoinage of 1816 The Great Recoinage of 1816 was an attempt by the British Government