This build is one of the earliest of Windows 3.1 (codenamed "Janus") builds, and certainly the earliest one available.
In terms of both, code and functionality, this build is not significantly different from Windows 3.00a, on which it was obviously based, however, it did add support for Screen Savers and TrueType fonts, among other things.
It was also by the time this build was compiled that Microsoft was starting to replace the old Windows 3.0 icons with newer, 3D style ones for Windows 3.1.
This build still uses the Windows 3.0 boot screen, but says 3.1, instead of 3.0.
