Oh, cool: 
"f you look at the back right-side pocket of your pair of Levis. You will see
that there is a red tab there. The majority of them will say LeVIS on them, if
you are lucky it will just have a ® on it. The reason for this is that Levis
actually has a registered trademark on the red tab itself so that no companies
can use it on their jeans. Therefore, they are required to put just the ® on
at least some pairs of jeans. So, 1 in every 50 pairs of Levis has the ®
instead of the LeVIS."

trueclothing.net/trueblog/?m=200711