Apple Desktop Bus (ADB) Mouse (A9M0331, 1986)

The Apple Desktop Bus Mouse was redesigned and named for its new ADB connector that was used in Macintosh computers from 1986–1998. This mouse featured low-profile blocky design with a flattened pentagonal side profile and a flat rectangular (slightly trapezoidal) bottom. It had a single button and tracked using a rubber ball.

I have three different variations of the ADB Mouse in my collection. One has a dark ring supporting the trackball, another has a light ring matching the color of the body of the mouse, and a third model uses a ring with an arrow.

The ADB port was a round, 4-pin plug that was used on the Apple IIGS (1986), Macintosh computers, and licensed for use on NeXT computers. The Apple Desktop Bus system was created by Steve Wozniak as a single connector for input devices that was inexpensive to produce. The Macintosh II and Macintosh SE were the first Macintosh computers to use the ADB port. 

Source: Wikipedia.com