Black Markings on end of Manny Ramirez Dodgers game used bat

[gamer35]

Does anyone have any clue what the black marks on the end of this Manny Ramirez 2009 Dodgers bat could be? I have seen other Dodger bats with similar black marks on the end of the barrel such as 2 of the Matt Kemps below but never to this extent. Perhaps from tapping the bat on an indoor hitting surface?

[ironmanfan]

Black marks come from hitting off a black rubber batting tee