 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.