This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
The 3.5 unidisk won't work on the earlier IIc unless the IIc has had a ROM upgrade. The Laser 3.5 is actually a Macintosh drive with the addition of an eject button. It isn't compatible with any Apple II unless it has a special controller card, which of course a IIc doesn't. By: Stephen Buggie