Convert from mark [English] to pound [troy]

Unit Definition (mark [English])
The mark is a traditional units of weight in various countries of Western Europe. In each country the unit equals 1/2 the unit corresponding to the English pound. Thus the French marc equals 1/2 livre, 8 onces or about 244.75 grams; the Spanish marco equals 1/2 libra or about 230 grams; the German mark equals 1/2 pfund or about 280.5 grams; and the English mark equals 8 ounces or 226.8 grams. The English unit was used almost entirely for measuring precious metals.

Unit Definition (pound [troy])
The pound [troy] is a second traditional unit of mass or weight. The troy pound, named for the French market town of Troyes, was the unit used in England by apothecaries and jewelers. The troy pound is divided into 12 ounces like the Roman pound. One troy pound is 373.242 grams, or exactly 144/175 = 0.822 858 avoirdupois pounds (13.165 72 avoirdupois ounces). The troy and avoirdupois pounds are connected by the grain: there are 5760 grains in a troy pound and 7000 grains in an avoirdupois pound.