The famous pose of Sean Connery holding a gun across his chest had to be redone at the last minute. The Walther PPK was left at the studio, but the photographer had an old air pistol in his car. The gun in the picture is the air pistol.
When Major Geoffrey Boothroyd wrote to James Bond creator Ian Fleming after reading "Casino Royale", he criticized Bond's use of firearms. He stipulated that Bond's Walther PPK was not as potent a weapon as the .44 magnum (used by Dirty Harry) and that a shoulder holster (as seen in Dr. No (1962)) does not provide as quick a draw as a belt holster (viz many Westerns).
The character of Q (aka Major Boothroyd) in the Ian Fleming James Bond novels is said to be based on Major Geoffrey Boothroyd, a gun expert who lived in Glasgow, Scotland. They share the same surname. Boothroyd wrote to Fleming about the James Bond character and his choice of firearms. Major Geoffrey Boothroyd can be seen with Sean Connery in this black and white 1964 short documentary.
James Bond creator Ian Fleming once wrote an article for the Sunday Times and Sports Illustrated about the Guns of James Bond.