Well, that's is a rare one then, and in remarkable shape. Having volunteered at a WWII aviation museum for years, I saw a number of these come through the doors from "family members", all of them claiming to have been real and wanting a proffer of gift form (form to get a tax write-off) to donate it to the museum. None of the ones I saw were real. I'm sure that most of you have seen the websites that show shirts in Japan with words or phrases that don't make sense. Well a lot of the flags like this one floating around are the American equivalent of that, sadly. So it's good to know that there are some real ones out there, and in museums where they belong.
Thanks for the translation and verification, Shinpachi-san!