These are the weights used for precious metals. The equivalents are 24 grains = 1 pennyweight; 20 pennyweights = 1 oz; 12 oz = 1 lb. The troy grain is the same as the avoirdupois grain, but the ounce is larger on the troy scale; 1 tr oz = 31.103 g; 1 avoirdupois oz = 28.35 g.