All unused U.S. postage stamps issued since 1861 are still valid as postage at their indicated value. Stamps with no value shown or denominated by a letter are also still valid, although the value depends upon the particular stamp. For some stamps issued without a printed value, the current value is the original value. But some stamps beginning in 1988 or earlier, including Forever Stamps (issued from April 2007) and all first-class, first-ounce stamps issued from January 21, 2011, the value is the current value of a first-class-mail first-ounce stamp. The USPS calls these Forever Stamps but the generic name is non-denominated postage.
all unused us postage stamps issued since 1861 are still valid as postage at their indicated value stamps with no value shown or denominated by a letter are also still valid although the value depends upon the particular stamp for some stamps issued without a printed value the current value is the original value but some stamps beginning in 1988 or earlier including forever stamps (issued from april 2007) and all first-class first-ounce stamps issued from january 21 2011 the value is the current value of a first-class-mail first-ounce stamp the usps calls these forever stamps but the generic name is non-denominated postage