The original publicity shots of Sean Connery holding a pistol was a bit of a blooper, as the gun he was holding was in reality just a Walther .177 caliber air pistol, as when Sean Connery went to the photo-shoot nobody had thought to bring a Walther PPK. One of the photographers practiced a bit of air pistol shooting. He had the airgun in his car, so he fetched it and that was what they used.
It was just a case of " Here you are Sean, now hold this gun and stand there "
No one, of course, told Sean Connery or the rest of United Artists production crew.....until much later, too late in fact as Sean Connery, holding this gun was used in ever publicity photo from 1962 until ' You Only Live Twice' was made in 1967.