\Troy\, n.
Troy weight.

{Troy weight}, the weight which gold and silver, jewels, and
   the like, are weighed. It was so named from Troyes, in
   France, where it was first adopted in Europe. The troy
   ounce is supposed to have been brought from Cairo during
   the crusades. In this weight the pound is divided into 12
   ounces, the ounce into 20 pennyweights, and the
   pennyweight into 24 grains; hence, the troy ounce contains
   480 grains, and the troy pound contains 5760 grains. The
   avoirdupois pound contains 7000 troy grains; so that 175
   pounds troy equal 144 pounds avoirdupois, or 1 pound troy
   = 0.82286 of a pound avoirdupois, and 1 ounce troy =
   117/175 or 1.09714 ounce avoirdupois. Troy weight when
   divided, the pound into 12 ounces, the ounce into 8 drams,
   the dram into 3 scruples, and the scruple into 20 grains,
   is called apothecaries' weight, used in weighing
   medicines, etc. In the standard weights of the United
   States, the troy ounce is divided decimally down to the
   1/10000 part.