Board Thread:Manga/@comment-5774380-20151009004044/@comment-26932251-20151009061534

174.65.63.177 wrote: Also Erwin could have been looking at his arm and saying, "something to hide" because maybe he is able to get his hands on that kind of technology. Interesting thought, I don't think it's accurate but in some ways at this point your guess is as good as mine.

Correct me if I'm wrong though but at this point the world within the walls doesn't even have a functional knowledge of electricity, so if Erwin had something fun like that, it would have to have been from the previous civilization before the titans (after all, post apocalyptic is the setting).