Take this passage from Agatha Christie's The Seven Dials Mystery. [Emphasis added]
"Do you think you could go out and buy me a pistol, Stevens?"
"A pistol, sir?"
True to his training, Stevens betrayed no hint of surprise.
"What kind of a pistol would you be requiring?"
"The kind where you put your finger on the trigger and the thing goes on shooting until you take it off again."
"An automatic, sir."
"That's it," said Jimmy. "An automatic. And I should like it to be a blue-nosed one—if you and the shopman know what that is. In American stories, the hero always takes his blue-nosed automatic from his hip pocket."
Stevens permitted himself a faint, discreet smile.
"Most American gentlemen that I have known, sir, carry something very different in their hip pockets," he observed. Jimmy Thesiger laughed.
In this passage, what is a "blue-nosed" gun?
In addition, in the 1930s, what would a fictional American gentleman be keeping in his hip pocket?