General Tomoyuki Yamashita Signature Stamp

I recently acquired a Philippines banknote signed by Japanese general Tomoyuki Yamashita. It dates (1945-1946) to when he was held in prison in Manila awaiting trial for war crimes. In addition to his two handwritten signatures, there is also a signature stamp. The assumption would be it is his as well. However, there is another example of his stamp while in prison. It differs from that on the note. Is it possible he had two. Might one be more "official" or formal? I am hoping the forum members can help.