While it may exist somewhere, the statement
Turing 4.1.2 for Windows - Unreleased version of Turing found when HoltSoft released the source code of Turing. May still be buggy.
does not imply that there was 4.1.2 source code released. It merely states that when
the Turing source code was released (whatever version that may have been), an unreleased version, 4.1.2, was also
found (though not necessarily the source code of it).
Or at least that's how I interpret it...