For centuries gold has been weighed in Troy Wt, grains, pennyweights and ounces. a grain is a small and precise unit of weight. Nowadays everone seems to want to weigh it in grams and fractions thereof. How many .258s does it take to make 31.1034768, or in easier figures 1 ounce? 24 grains = 1 DWT 20 DWT =1 ounce or 480 grains to a ounce. Simple. Troy weight is the international and traditonal unit of weight for gold and has been since the 5th century. I can't even visualise the size of a piece of gold that weighs .258 gms. Maybe I'm old fashioned but Troy just seems simpler to me. Ft Knox even uses the troy unit of Wt.............JMO