Jien on AR15.com posted s scan of article from Japanese magazine 'Gun'. It shows R1, very similar to AR-10 and how it progresses to Howa Type 64 rifle.
http://www.ar15.com/forums/t_1_5/1807712_Japanese_made_AR_10_Variants__Japan_s_First_Experimental_Rifle_after_WW2.html
Frm: Ar15.com