I've had a Ruger Super Single Six (adj sights) Convertible (.22WMR cylinder) since the 80s. I'd have to check but I think the grip frame and maybe the ejector rod housing are aluminum.
For the money, I think its the best .22 SA you can get. I don't use the WMR cylinder, haven't fired two full boxes of the stuff since I got the gun (new), for me, .22WMR is just too expensive for what you get (and that was back when it was $6 a box!)