APF Imagination Machine floppy disk
The APF Imagination Machine floppy disk was the disk drive for the late-1970s personal computer / game console from APF, a company that previously made calculators. The computer came with a tape drive, with the floppy disk drive being an optional add-on which cost $350 for the drive and $200 for the drive controller cartridge to run it. It is difficult to find online documentation for the disk drive, its disks, and the associated APF Imagination Machine disk file system, since these are not documented in the manuals for the computer itself as they were not included with it. (If somebody has the manuals for the disk drive, it would be helpful to scan and upload them somewhere that they can be linked here, such as the Internet Archive.) The disks were 5 1/4" floppies with a rather meager storage capacity of 72 KB, according to one site writing about them. (However, emulated disks in APD format are 64 or 68 KB, and seem to consist of 272 sectors of 256 bytes each.) One use for it was to store BASIC programs.
The APD format is used to store raw data from APF disks for use in emulators.