DO NOT REMOVE or NOT TO BE REMOVED.... that is the question.

Today I purchased a Webley Senior at Kempton Park. Fantastic show and great stuff there.

I am a complete newbie to Webleys, and was wondering why my new piece has NOT TO BE REMOVED on the rear of the pistol, whereas, many I have been looking at on line have the words: DO NOT REMOVE. Can anyone enlighten me?

Best regards to all.