Silver has long been used as a monetary metal, and is available in many forms both old and new.  It is also available in "bullion" forms, that have no official legal tender value.

American Eagles	Maple Leaves	Vienna Philharmonic
Walking Liberty Halves	Kennedy Half Dollars	Franklin Half Dollars
Mercury Dimes	90% Silver Bags	40% Silver Bags
1 Ounce Bars and Rounds	10 Ounce Silver Bars	100 Ounce Silver Bars