hard disk
The M55302/4-02 is a part of the Winchester hard disk system, which were designed in the 1970s to store large amounts of data (typically more than 10MB) on rotating platters. This particular part is a frame assembly, which houses the components of the drive, including the printed circuit board assembly, the read/write arm assembly, spindle assembly, and other components. It is constructed from aluminum with a aluminum anodized finish, and also includes side panels, screws, and related hardware.