I'm with TinyRedLeaf. Those are the real-life kanji on the Sen-Gauge, albeit stylized.

It makes hard to know how to take them. All of the Ninja Kanji are different from their real life versions, and none of the kana really resemble either of the real-world sets, but all of the Samurai kanji are the same? It's not outside the realm of possibility, obviously, but it is a weirdly-outlying case.