Pennyweight Troy weights were defined in such a way that the old Tower pound came out to exactly 5400 Troy grains (also known as barleycorns), the Tower pennyweight Troy grains (and thus approximately 1.46 grams). After 1527, the English pennyweight was the Troy pennyweight. of 24 Troy grains. Thus the Troy pound, ounce, and pennyweight, with their definitions given in terms of the Troy grain instead of in terms of the Tower grain, were 1/15 or 6.667% more than the Tower equivalents. The Troy pound and the pennyweight lost their official status in the United Kingdom in the Weights and Measures
Troy weight system. The origin of the troy weight system is unknown. Although the name probably comes from the Champagne fairs at Troyes, in northeastern France, the units themselves may be of more northern origin. English troy weights were nearly identical to the troy weight system of Bremen. (The Bremen troy ounce had a mass of 480.8 British Imperial grains.) An alternative suggestion is that the weights come from the Muslim domains by way of the Gold Dirhem (47.966 British Imperial grains), in the manner that King Offa's weights were derived from the silver Dirhem (about 45.0 British grains). According to Watson,