Thanks, Rory. The only reason I ask is my 1951 R in 300 has Pre War flat top sling studs. Every Pre War RS I've seen has the forearm stud on the forearm screw. My studs are exactly where the two eyes are on your pictures. I'm sorry if I call the studs/eyes the wrong name, to clarify, I call the old small sling attachments "Eyes". The eyes on my 1950 R look like the ones in your picture, similar to the eyes on my 1912 H. I call the big round flat top attachments "Studs". I put a mic on the center of the forearm screw, to the center of the Eye on the 1950 R. Off the top I think it was 2.42". Then I measured from the center of the forearm screw to the center of the stud. They were exactly the same. Bubba probably just used the same holes? I've never called my 51 with the studs an RS, never will. But, I've always thought it was interesting that if Bubba put the studs on, it looks like he tossed a set of factory eyes to put the more expensive studs on the rifle. When I bought the rifle it had a tang sight on it, but I couldn't afford it. I forget if it had a rear sight, it has a blank in it now. I think it has the same front sight as my 1950 R, in 250. Anyway, I've been thinking of selling the one with the studs, several people have offered me pretty good money for the studs. So, if I sell it, I might pull the Pre War studs and put a set of eyes on it? It's a nice rifle with good case colors still on the outside of the lever. Just because I've dreamt that this was the ever elusive Post War RS, if we could letter it, I'd drop $75 on it.
The 1951 catalog says the RS has the same specifications as the 99R except for sights, and the 99R had sling eyes.
They were still selling the flat topped studs separately in 1951 (4A studs & swivels, 7/8" or 1 1/4", $4.75).
So it looks like the owner of your rifle upgraded the studs.
