At the beginning of Wonder Woman, we saw Diana going to her day job at the Louvre, where she studies and analyzes antiques. While in her office, she received a delivery from Wayne Enterprises; the photograph of her from World War I standing with Steve Trevor, Sameer, Charlie and Chief. As you’ll recall if you’ve seen Batman v Superman: Dawn of Justice, Diana was investigating Lex Luthor because he possessed this photograph, hence how he knew she was something “special,” i.e. one of Earth’s metahumans. Bruce later found a digital copy of this picture, and he was understandably shocked to learn that the woman he had just met was alive 100 years earlier and looked exactly the same.