This a standard 2-button ball mouse. A few 64DD games support it:
- Mario Artist: Paint Studio
- Mario Artist: Talent Studio
- Mario Artist: Polygon Studio
- Mario Artist: Communication Kit
Most other N64 games see the mouse as a controller, and a few of them are playable like this. Mouse movements register as analog stick movements. The left button maps to the A button, and the right mouse button maps to B.
There is a single microcontroller that handles everything.
This mouse appears to be based on contemporary Mitsumi PS/2 mice, which have nearly identical guts. Closest match is the ECM-S3902