128K through Plus
Fanny Mac (System Saver). Made for the Macintosh 128K, 512K, 512KE and Plus models.
Slide it into the handle area at the top of your Mac, plug the short cable into it and the long cable into an outlet. The fan draws air up through the Mac. There is a switch on the top to turn it on. The Fanny Mac sits inside the handle area so it is more flush with the top than a Kensington System saver.
While it may or may not sit on top of other compact Macs, they don’t have the ventilation holes. Newer models (Macs) also came with a built in fan.
The top of this one is severely discolored (common from what pictures I can find). Works great!