Windows 3.0 build 12

Windows 3.0 build 12 is an unleaked build of Windows 3.0, which was found in an antitrust document dated 8 February 1989. from build 55 contains the following string: Microsoft Windows Old Application Support Module (3.00.14.20jan89) This suggests that build 14 was already compiled around 20 January 1989. Therefore, build 12 was almost certainly also compiled in January 1989.

This build is also mentioned in the source code for the calculator of Windows.