Vacheron Constantin

Earlier today, I was looking at the back of my Malte Manual Chronograph with a loupe (an undertaking that non-patrons of this site might think is crazy). In looking at the movement -- which is really beautiful -- I noticed an intersting item on the plate just beneath the balance wheel. (Please excuse my technical terms if they are incorrect.)

 
On the plate, there is the designation "1141" in a rectangle. I believe that is Vacheron's number for the Lemania-based movement used in the watch. Just above that, and more directly underneath the wheel, there is a maltese cross-looking item with the letters "LWO" in it. Can anyone tell me what LWO stands for?

Thanks,
Bob