I don't think one so marked, with a period mark has yet to be found. There are not any imported arms {known to date} which have a legitimate "CS" stamp.
The "CSA" stamped on your gun is done with individual dies, in a more modern font, stamped on top of the pitting. It is very poor attempt to increase the value of the gun, probably to an uninformed buyer.
In the world of Confederate collecting, Fakes abound. The collector had better know what he's looking at, or be prepared to have a display of the stuff on a "Wall of Shame".