movie trivia: fun and games

Some years ago in a shop dealing with historic documents, a photo still from Casablanca (1942) was found, showing Rick sitting at the chess board. Accompanying the photo was a letter from Humphrey Bogart to a friend in New York, indicating a specific chess move. The document dealer explained that the chess game in the movie was a real game Bogart was playing by mail with his friend during the course of filming.