I know a lot of "old timers" around here who still use dwt for weighing gold, but having working as a gold assayer most of my life I've found the most reliable weight is in grams. I've worked closely with the major refiners, Johnson Matthey, Engelhard, Handy & Harman, etc., and I've never seen one who didn't use grams exclusively for the standard weights, sometimes to four decimals. We weighed assay prills (beads) down to a microgram on very sensitive microbalances to achieve correct assay-ton fusions. An assay-ton is 29.1667 grams, rounded to four decimal places in this case. I believe grams are more accurate when it really counts, and I know of no professionals who use anything else.