Monex silver coins are pre-1964 United States currencies of quarters or dimes that contain 90 percent silver, states the Monex website. Investors can purchase 90 percent silver bags by calling Monex at 800-997-7859 as of 2015.
Coins that were minted before 1965 contained 90 percent silver, whereas coins minted after 1965 are primarily composed of cupronickel, according to Monex. The 90 percent silver bags offered by Monex contain a $1,000 face value of coins, and they are composed of either 10,000 U.S. dimes or 4,000 U.S. quarters that were minted prior to 1965. The coins are still worth at least their face value as of 2015, whether or not the price of silver fluctuates, states Monex.