I Googled "Unconditional Surrender" and Grant and found a Wikipedia entry that says that "Unconditional Surrender Grant" was a nickname for him. "Buckner's surrender of over 12,000 men made Grant a national figure almost overnight, and he was nicknamed 'Unconditional Surrender' Grant." Therefore, you guys are correct and it is Ulysses S. Grant. (The info is in the paragraph under the heading Battle of Belmont, Henry, and Donelson.)

Wikipedia also says that ; "In 1876, Grant helped to calm the nation over the Hayes-Tilden election controversy; he made clear he would not tolerate any march on Washington, such as that proposed by Tilden supporter Henry Watterson." Perhaps that is what the "76" in the etch refers to, or maybe I'm just seeing things that aren't there...