Group of three items signed by Albert Einstein's family and associates, including: a fine copy of his famous 1939 letter to President Franklin D. Roosevelt encouraging the development of the atomic bomb (featuring his facsimile signature), two pages on two adjoining sheets, 8.5 x 11, bearing an affixed stamp honoring Einstein with first-day cancel, signed at the head in blue ballpoint by his stepdaughter, Margot Einstein, and his secretary, Helen Dukas; and a first day cover with a cachet honoring Albert Einstein, signed in blue ballpoint by Margot Einstein and Helen Dukas; and a typed statement signed by Einstein's friend, the Nobel Prize-winning physicist Eugene Wigner, one page, 8.5 x 11, offering his recollections of Einstein's letter to FDR. In overall fine condition.