If I understand your description correctly, I also have these marks on a S&W PC Schofield that I bought about a year and a half ago. I had assumed that the former owner had shot some higher loads through it and caused the cylinder to impact the latch. That and the pistol had the loosest screws that I have ever seen led me to this conclusion.
I have a couple other S&W's that have only been used for CAS and they do not show this sort of damage at all.