Beginning with System File version 4.2, Apple began bundling software in release bundles, instead of as independent System, Finder, and device support files as they had done for all previous versions.
In October 1987, Apple released System Software 5.0, a software bundle which included System 4.2, Finder version 6.0, MultiFinder 1.0 and LaserWriter version 5.0.
System Software 5.1, released in November 1987, included System 4.3, Finder version 6.0, MultiFinder 1.0 and LaserWriter version 5.1.
No version of the System file was ever numbered "version 5".
Sources and References
There was never an official Macintosh system software called "System 5".
|Macintosh system software|