Yup, the Speed Sixes are most common. Here is some eye candy of the square butt Service Sixes with both types of recoil shields.
I've got a blue 4" too, but don't recall ever taking pics. I do have the prototype 9mm which was built on a lowback 4" Security Six, but there were no production 9mm Security Sixes that I am aware of.
Then here is a 9mm Speed Six that doesn't need moon clips, it has the Pilorget extraction system. Ruger didn't make many of these because the patent holder on that design was a French guy who wanted too much per gun for the rights.