This 2017 Windsor Castle medal cover is a Royal Mail first day cover. It celebrates world's oldest castle resided by the Royal Windsor's and hosts a medal by the Royal Mint and Royal Mail commemorative stamps showing facets of Windsor Castle. The medal has the inscription It is the most romantic castle that is in the world - Samuel Pepys 1666 . Cancelled postmark Celebrating The World's Oldest Castle Windsor Castle Windsor 12th February 2017.