What is the difference between a silver certicate and a US note?

US Notes were among the first forms of currency issued by the Treasury Department. They first appeared in 1862 during the Civil War, and were printed up till 1968, although the last ones were actually dated 1966. US Notes were issued directly by the Treasury and were distinguished by their red seals and serial numbers. Like Federal Reserve Notes, they didn't have any precious-metal backing; their value was contingent on the stability of the US government. Production was discontinued only as a money-saving move to consolidate all currency production and administration under the Federal Reserve.

Silver certificates were bills backed by silver on deposit with the Treasury. They could be issued only in quantities that didn't exceed the total value of that silver. At one time, when the price of silver was fixed by the government, it was possible to exchange these bills for silver bullion as well as coins. When the price of silver was deregulated in the mid-1960s silver certificates were discontinued and the practice of exchanging for metal ended. Most silver certificates are recognizable by their blue seals.

Neither of these types of currency has been officially demonetized or withdrawn, so technically they can still be spent at face value. However most of them are worth more than that to a collector, although late-date notes only carry a small premium.