Troy Weight, a scale of weights used in England and the United States for weighing gold, silver, and jewels, and in trying the strength of spirituous liquors, and legally established in both countries for determining the weight of coins. The derivation of the term is uncertain. In 1828 a standard troy pound in brass brought from England was declared by act of congress the legal standard of the United States mint. It is equal in weight to 22*815676 cubic inches of distilled water at 62° F., the barometer being at 30 inches. It contains 5,760 grains, of which 24 make a pennyweight, 20 pennyweights an ounce, and 12 ounces a pound. It is the standard of the imperial system of weights in England, and from it is derived the avoirdupois pound, which contains 7,000 troy grains; and 1 lb. avd. = 1-2152777+ lb. troy. (See Avoiedtj-pois.) It is identical with the pound of apothecary's weight, and the ounce and grain of these two weights are also correspondingly the same. The pennyweight subdivision of troy weight, determining the weight of the silver penny, was established in 1266, as equal to the weight of 32 grains of wheat taken from the middle of the ear.
As the kings of later times found it expedient to reduce the value of the penny, this reduction was accompanied by a proportional diminution in the number of grains of which it was composed. A troy weight was established in 1618, the pound of which weighed 1.321 pound troy. This is now abolished by law.