The German James Bond Club, Bondklub Deutschland, has just published an article about the Beretta on the Teaser Poster of Die Another Day.
As you remember, there was speculation about why filmmakers choose a Beretta, neither a Walther. Well, the BKD has solved this mystery – and it has nothing to do with the plot directly.
Insider at Walther said that the use of a Baretta is just a simple mistake, and Walther confirms that Bond will use a Walther P99 in Die Another Day. So why can we see a Beretta on that poster? The BKD insiders could not confirm neither deny that Spoiler Warning (Highlight To Read) the villains are going to use a Beretta, but as said above, on the Teaser Poster, it's just a mistake.
Possibly, the photographer who made the taking, used a Beretta, because he didn't have a Walther to mug.
The only curiosity: nobody at MGM noticed the mistake.
In the same note the BKD confirms that also in Germany the Teaser Trailer for Die Another Day will air together with "Star Wars: Episode II".