Did Ruger ever mark any of their grip frames with just Alcoa in a rectangle and G2. It looks like an XR-3 Red but I didn't have time to try on a set of grips to see if they fit.
Much confusion surrounds the Ruger Single Action Grip Frames. Lucky for us, Boge Quinn has graciously allowed us to "link" a page from their gunblast.com web site. https://www.gunblast.com/Hamm_Ruger-SA-GripFrames.htm