Hi,
I searched for patents assigned to Mitsumi that might be relevant to the Disk System.
The most interesting/useful is a Japanese patent, JP 63004477 (A) dated 1988-01-09. The English title for that is "File management system for magnetic disk", and there are diagrams showing the header, directory, gap, id, sector data, sync, crc etc., which could be similar to the FDS disk layout. Maybe someone who can read Japanese would like to take a look? There could be some useful info there.
US patent 4665453, filed on 1984-04-25: "Floppy disc recording and/or reproducing apparatus" appears to cover an alternative top-loading drive mechanism which wasn't used for the FDS. This page has a picture of a drive with that type of mechanism.
US patent 4573572 "Recording disc cartridge" covers construction of the disk, not particularly useful, as is D287597 "Magnetic disc cassette" covering the external design.
US patent 4669009, filed on 1983-10-25: "FLOPPY DISC RECORDING AND/OR REPRODUCING APPARATUS HAVING A LOADING MECHANISM FOR LOADING A CARTRIDGE WHICH ACCOMODATES A FLOPPY DISC" actually seems to be a 3" floppy drive, so not relevant here.
I searched for patents assigned to Mitsumi that might be relevant to the Disk System.
The most interesting/useful is a Japanese patent, JP 63004477 (A) dated 1988-01-09. The English title for that is "File management system for magnetic disk", and there are diagrams showing the header, directory, gap, id, sector data, sync, crc etc., which could be similar to the FDS disk layout. Maybe someone who can read Japanese would like to take a look? There could be some useful info there.
US patent 4665453, filed on 1984-04-25: "Floppy disc recording and/or reproducing apparatus" appears to cover an alternative top-loading drive mechanism which wasn't used for the FDS. This page has a picture of a drive with that type of mechanism.
US patent 4573572 "Recording disc cartridge" covers construction of the disk, not particularly useful, as is D287597 "Magnetic disc cassette" covering the external design.
US patent 4669009, filed on 1983-10-25: "FLOPPY DISC RECORDING AND/OR REPRODUCING APPARATUS HAVING A LOADING MECHANISM FOR LOADING A CARTRIDGE WHICH ACCOMODATES A FLOPPY DISC" actually seems to be a 3" floppy drive, so not relevant here.