I am interested in identifying this prop airfoil due to its uncommon high .92% efficiency (the best metal props are closer to 83-87%). I have done an exhaustive search for it. It is labeled "NACA RML 9 G 06a". I do not know where I originally got this plot and therefore have no way to know what "ref 3" is.
It does not appear to be a airfoil number and a google search doe not return any "NACA RML" however I have a library of about 2000 "NACA RM" which refers to NACA Research Memos; perhaps the additional "L" means "Letter(s)".
I can find NACA reports starting with "RM G-10" but no G-9. I have also searched for derivatives of "06a" in an airfoil number. I would appreciate any assistance in identifying this airfoil.