System 3.1

System 3.1, published a month after System 3.0, was released alongside Finder version 5.2 as a part of Macintosh Printer Installation version 1.0. It had serious errors. Use of System 3.1 was seriously discouraged, and use of 3.0 was encouraged until 3.1 was replaced by System 3.2 four months later.
 * Released: February 1986

External References

 * Early Macintosh