Character mistake: The telegram from Mount Wilson Observatory mentions "extraordinary electric waves." The Italian dub also makes up that it was sent from "Dr. Johnson," when it is in fact signed "William Johnes."
Revealing mistake: Throughout the movie (for instance, at its first appearance when it drives towards the camera, or when it drives off), Sonny Chiba's vehicle (or rather, its shell) is made of cardboard; the front creases, the fins wobble.
Answer: Your question was intriguing, so I did a little Internet research. While there's plenty of conjecture, nobody seems to know what this is about. There is some reference to Hitler's "Mein Kampf" being published in Japan for the first time in the early 1960s, around the time the film was made. Some speculate it was some type of advertising for the book (early product placement?) while others believe it could be a symbolic act of blowing up Hitler's ideals and could explain why it was misspelled.
raywest ★
Ray's answer on the subject is already exhaustive. I'll add for further clarification that the advertising apparently was for "Den blodiga tiden", or, well, Mein Kampf, Erwin Leiser's documentary about the infamous book. I can't find the primary source for it, but it appears credible since the release date of the documentary in Japan was in January of the same year. Also, I do think that given the egregious misspelling, someone should post it also in the mistakes section, even if it was not made by the moviemakers, technically.
Sammo ★