Pound (mass) 6, 12, 18, 24, 32 and 42 pounds; 68-pounders also exist, and other nonstandard weapons use the same scheme. See carronade. A similar definition, using lead balls, exists for determining the gauge of shotguns. Pound (mass) The pound or pound-mass is a unit of mass used in the imperial, United States customary and other systems of measurement. Various definitions have been used; the most common today is the international avoirdupois pound, which is legally defined as exactly , and which is divided into 16 avoirdupois ounces. The international standard symbol for the avoirdupois pound is lb; an alternative symbol is
Pound (mass) 6750 troy grains, or 9600 Tower grains, derives from this pound, as 25 shilling-weights or 15 Tower ounces, for general commercial use. Multiple pounds based on the same ounce were quite common. In much of Europe, the apothecaries' and commercial pounds were different numbers of the same ounce. The Tower system was referenced to a standard prototype found in the Tower of London and ran concurrently with the avoirdupois and troy systems until the reign of Henry VIII, when a royal proclamation dated 1526 required that the troy pound to be used for mint purposes instead of the Tower pound.