Gives any computer with a USB port a full-fledged Apple Desktop Bus. Installs driverlessly under Windows and works with mice, joysticks, keyboards and tablets. Probably works with other stuff too.
Unless they've come down a lot in price, methinks you got it for a couple of bars, much less a song. I really like your clear one, IIRC, mine's some dreadful blue-green excuse for a color.
Mine is the earlier Bondhi color. Got it for free from a guy on flickr who didn't need it. Will be using it on the G4 again once I source another working M0116 or M0115.