All United States silver coins dated 1964 and earlier are 90 percent pure silver. Though these coins are considered legal tender, the value of their silver content is more than the face value of the coins. For those investors interested in silver, these coins offer an excellent strategy because they can be bought with little premium. You could also sell such coins and make a nice profit if you purchased them at a time when silver had less value. In the 1970s, bags of these coins were frequently referred to as “junk silver bags,” because they contained everyday circulated silver coins without any rare ones.