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
Presolar grains to a sufficiently high level to measure isotopic abundance ratios within micron-sized grains. Ernst Zinner became the undisputed leader of SIMS applications to microscopic grains, earning him historic acclaim. Presolar grains are the solid matter that was contained in the interstellar gas before the Sun formed. The stardust component can be identified in the laboratory by their abnormal isotopic abundances and consists of refractory minerals which survived the collapse of the solar nebula and the subsequent formation of planetesimals. To meteorite researchers, the term presolar grains has come to mean presolar grains found in meteorites, which consist overwhelmingly of stardust.