I suspect you are right and the Mississippi Richards are all the same individual. With that taken into consideration, if you narrow it down by the common usage of "T.W.Richards" (people are creatures of habit when it comes to their names)in the offical records. Then consider, it's most likely only an Officer would have his name professionally engraved on his revolver (and unlikely Infantry enlisted men would carry such a large, heavy revolver), add in the units physical proximity to the Tenn. area early in the war. And it seems Captain T.W. Richards of the 9th Battalion Mississippi Sharpshooters is the most likely canidate. I don't think I could add any more rationalization to this if I tried, but it does sound reasonable.

JH