No contemporary physical description of William Shakespeare is known to exist. The two portraits of him that are the most famous (both of which may be posthumous) are the engraving that appears on the title-page of the First Folio, published in 1623, and the sculpture that adorns his memorial in Stratford upon Avon, which dates from before 1623. Experts and critics have argued that several other paintings from the period may represent him, and more than 60 portraits purporting to be of Shakespeare were offered for sale to the National Portrait Gallery within four decades of its foundation in 1856, but in none of them has Shakespeare's identity been proven.