Up in the northeast, these RL's and RLS's are highly sought after for woods rifles so they bring a premium. I wouldn't call an RL scarce unless it was 243 of 250-3000. The RLS is much more uncommon, especially in the short action calibers.
I assume the 18" was measured from the receiver ring to muzzle and does not include the 1/2" of barrel inside the receiver? With that barrel length I suspect it is it an RSI dropped into an RL stock. Just as I did with my 7x57 RSI.
can't call anymore now cost you 10 but formal letter see sticky in the Ruger And Other Firearm Collecting area. I don't think that sn would have had a red pad either bit I could be wrong