It is Win3.1 Second edition so to say.
There is also a second edition of Win95 and Win98.

The one Windows sticking out however is Windows 8.1. Treated like some "second edition" by Microsoft, it internally is handled like a complete new Windows. (Win 8 = NT 6.2, Win 8.1 = NT 6.3)

And that's not what I'm saying, that's what someone put on Wikipedia