Norman Rockwell’s 12 best loved post covers from 1916 – 1960 Certificate of authenticity Numbered 1277. This set of 12 silver bars is a must-have for any collector. The bars are composed of 0.999 fine silver and each bar weighs 1 oz. The bars have a total precious metal content of 12 oz. The set was manufactured by Hamilton Mint in the United States in 1975. The bars are a great addition to any collection and are sure to impress.