The City of Winchester is fortunate to have in its vault the oldest surviving set of standard weights, the oldest standard yard measure, and a fine collection of other ancient measures and weights. These standard weights and measures were used to measure the goods they sold, as well as the weights and measures used by merchants to measure the goods they sold. This promoted both government taxation and fair trade.
To trace the origin of the term "Winchester measure," it is necessary to go back to Anglo-Saxon times, when during the reign of Alfred the Great (A.D. 871 - 899) Winchester began to play an increasing role in the administration of the kingdom and as a center of trade. In the subsequent reign of Edgar the Peaceful (A.D. 959-975), it was decreed that all measures should conform to the standards kept in Winchester and London. From that time the bushel and its parts - pecks, gallons, quarts, and pints - became known as the "Winchester measure" and were used to measure all grain and agricultural products until they were replaced by the imperial measure (about 3% more) in 1824. However, the old Winchester bushel is still used in the United States.
The Troy weight
The Troy weight is the oldest known English commercial weight, the name of which is thought to have come from the French city of Troyes, which was an important trading center back in the early Middle Ages. Under this system, 1 troy pound = 12 ounces = 240 pennyweights (dwt) = 5,760 troy grains; traditionally a troy grain is equal in weight to a grain of barley. The earliest weights were derived from seeds, so the terms "grain" and "carat" are still used today: "grain" came from the use of wheat grains, and "carat" came from the seeds of the carob plant. Troy weights are now used only for precious metals and stones.
The weight of Avoirdupois
The Avoirdupois weight began to evolve progressively from the Troy weight in the late 13th and early 14th centuries. The term comes from the Old French avoir de pois, meaning "goods of weight," and evolved from the idea that quantity of goods, not weight, was involved in trade. Under the Avoirdupois system, 1 pound = 16 ounces = 7,000 grains, and 14 pounds equals 1 stone. It is the Avoirdupois system that is referred to when talking about the imperial system.
Weight of Wool
As mentioned, the Winchester weights and measures are standards for checking the conformity of traded goods, and during the medieval period in England, one of the most important trade goods was wool. By 1421, customs duties derived from wool alone accounted for 74 percent of all customs revenue in England. Like the size of the pound sterling, the size of the stone also varied, but in 1340, during the reign of Edward III, the stone was set at 14 pounds sterling. This may have been done to match the measures used in some of the trading centers of continental Europe, such as Flanders, and thereby facilitate trade. Perhaps it was this change that made the Avoirdupois system preferable to the Troy system. Edward III decreed that a bag of wool, which was defined as 2 weights, was to be 26 stones or 364 pounds.