4c Abraham Lincoln plate proof
The definitive series of 1954-68 included Abraham Lincoln on the 4¢ value. When it was originally issued, this stamp paid the 'additional ounce' rate for surface letters to Europe (5¢ for the first ounce plus 4¢ for each additional ounce). Then, on August 1, 1958, the domestic first-class letter rate rose from 3¢ to 4¢, and this became the most heavily used stamp in America literally overnight! The Liberty Series, as the 1954-68 issue is known, were intended to have "warm portraits" of their subjects as opposed to the customary busts. The design of this stamp was adapted from a 1917 portrait of Lincoln by Douglas Volk in the National Gallery of Art, Washington, D.C.