Hello,
I have about 8 or 9 YSL Mombasa bags (I think more, but around that...haha) and some seem to have the metal top piece engraved with YSL and others don't. For example, I have a couple of the smaller Mombasa's (two of them I purchased at the same time) and one is engraved with YSL and the other isn't.
I sincerely hope this helps! best wishes, BeautifulBasics