Mac System Software 1.x

There are some early builds of Mac System Software 1.0, one of the builds is on a Twiggy floppy disk which was found alongside a Twiggy Macintosh. There are only 2 releases of Mac System Software 1.x which are 1.0 and 1.1g. There is an earlier version of the Finder on the Guided Tour that came with the original Macintosh.