Thanks for that, model70man. Just goes to show that one should never just assume, as I assumed it meant "sights". It's a lesson that one would think I would have learned by now. But...
You're welcome Sir. Somewhere I have a large poster from Ruger that I received from them when I had an FFL back in the day that explains the model designations. I owned a Liberty model ST but unfortunately got rid of it. I kind of liked that round top because it would take scope mounts for a M700 Remington.