Interesting, but how did you conclude that Leiter wore a Sub?
In the Connery films, I only ever recall catching the briefest glimpses of Leiter wearing something that looked to be on a black strap. In fact, it was Leiter who, in I believe Thunderball, commented to Bond that, "I see you're still wearing that old wristwatch of yours with the big phosphorous numerals". Had Leiter been wearing a Sub, I would expect a comment citing the similarity between his & Bond's watch. No?