The first legal definition of sterling silver appeared in 1275 , when a statute of Edward I specified that 12 ounces of silver for coinage should contain 11 ounces pennyweights of silver and pennyweights of alloy , with 20 pennyweights to the Troy ounce .
The first legal definition of sterling silver appeared in 1275 . A statute of Edward I specified that 12 ounces of silver for coinage should contain 11 ounces 2 + pennyweights of silver and 17 + pennyweights of alloy , with 20 pennyweights to the Troy ounce .