In Colonial times, pewter was known as “the poor man’s silver” because it had some of the attributes of silver without the expense. When oxidized (like our buttons), pewter has a rugged appearance.
Pewter is a metal alloy comprised of at least 90% tin, with the remainder copper, antimony, or bismuth. The alloyed metals provide strength and color tints to the tin base.
For more information on jewelry standards, you can read “Guides for the Jewelry, Precious Metals, and Pewter Industries” at www.ftc.gov.