The American Pewter Guild (APG), The American Society for Testing and Materials (ASTM) and the Federal Trade Commission (FTC) all worked together to come up with a definition of what pewter is. Their consensus? "A metal alloy product of which the chemical composition shall be not less than 90% Grade "A" Tin, with the remainder composed of metals appropriate for use in pewter."
Pewter, which is an alloy of 85–90% tin with the remainder commonly consisting of copper, antimony, bismuth, and sometimes lead and silver, has been used for flatware since the Bronze Age. [See Tin]