Finally, some one else asked this question. I had a whole thread about it some time ago.
http://smith-wessonforum.com/smith-w...appened-v.html
Here's how it wrapped up: The "V" stands for Stainless and the "E" stands for enhanced. The SW9E was part of the original production of enhanced Sigma's, you could opt for the SW9E with melonite coated steel slide and barrel or the SW9VE with the stainless steel slide and barrel. The SW9VE was more popular and they dropped the SW9E. Then S&W came out with the Allied Forces Model, which is melonite coated stainless steel slide and uncoated stainless steel barrel, hence it still having the SW9VE designation. The SW9E's are seemingly rare, but you do see them from time to time.
I cannot advise if S&W ever used carbon steel on any Sigma model, but I have never heard of them doing so.