The Disk
The first variation of the Disk II introduced for the Apple ///, called the Disk III (A3M0004), used the identical drive mechanism inside a modified plastic case with a proprietary connector. With some modification both drives are interchangeable. Though Apple sought to force the purchase of new drives with the Apple ///, many former Apple II users quickly devised a way to adapt their existing and cheaper Disk II drives, however only one external Disk II was supported in this manner. The Disk III was the first to allow daisy chaining of up to three additional drives to the single 26-pin ribbon cable connector on the Apple ///, for a total of 4 floppy disk drives – the Apple /// was the first Apple to contain a built-in drive mechanism. The Apple III Plus changed its 26-pin connector to a DB-25 connector, which required an adapter for use with the Disk III.