Macintosh II PC Drive Card
This is a NuBus card which appears to be a controller for the external PC disk drive kit.
The Macintosh II PC Drive Card provides the link between an Apple Macintosh II personal computer and the Apple PC 5.25 Drive. With this hardware and the Apple File Exchange program (included), you can convert many standard MS-DOS data files so they can be used in Macintosh applications. You can also convert Macintosh files into the MS-DOS format.