JIS are Japenese steels. They may have an equivalency to a P-1 material but is not listed, (to the best of my knowledege). I also checked an ISO Document we put together; ISO TR 20173 - 2005, which lists many of the weldable materials from several countries and this particular steel wasn't listed in there either.
When in doubt, ask your engineer to make a determination. It should be easy enough to look at the chemistries and tensiles and pass Holy water on it if listed as an acceptable material for the Project. One kicker may be that you'd have to do a separate WPS showing it as an unlisted material... if you're required to comply with ASME IX or D1.1.
Haven't seen you around in a while, are you still in the Great Pacific NW?