Wow, I've been trying to research this plane (looks nice!) and am coming up with incredibly little! I did find, however, that Hirobo made these planes in the '80's and they were marketed/sold by Altech and Model Rectifier Corp. Maybe you can give them a ring/email and see if there's any info available:

http://www.modelrectifier.com/contactus/index.asp

Let us know how it turns out!