Macintosh 512Ke (1986)
The Macintosh 512K enhanced (512Ke) was introduced in April 1986 as a cheaper alternative to the top-of-the-line Macintosh Plus, which had debuted three months previously. It was the same as the Macintosh 512K but with the 800K disk drive and 128K of ROMused in the Macintosh Plus. Like its predecessors, there was little room for expansion. Some companies did create memory upgrades that would bring the machine up to 2 MB or more. It is the earliest Macintosh model able to run System 6 OS. It is also the earliest Macintosh model that can be used as an AppleShare server, and with a bridge Mac, communicate to modern devices.
via Wikipedia: http://en.wikipedia.org/wiki/Macintosh_512Ke