I thought this was fun; stumbled upon it while looking for what words of wisdom Fred had to share about the format of 3" disks:
https://books.google.com/books?id=7D0EAAAAMBAJ&pg=PA86&lpg=PA86&dq=3%22+floppy+disk+format+fred+cisin&source=bl&ots=b3iHCeqJzB&sig=ACfU3U19DoXha-0sh2fqm26M72Z1tlKLXw&hl=en&sa=X&ved=2ahUKEwjsivXd75XmAhURLX0KHYL0BBkQ6AEwAnoECAoQAQ#v=onepage&q=3%22%20floppy%20disk%20format%20fred%20cisin&f=false Hopefully Fred will see this and tell me whether the 3" disk format was MFM or GCR given that the Orwellipedia says the 3" disk format was initially designed to work with the Apple ][ floppy drive interface. https://en.wikipedia.org/wiki/History_of_the_floppy_disk?fbclid=IwAR2atb2Z_j_-DVNLTT1eqAZLw4ajB9s0LxzWgSMQoyEoi0_5Yy1KuNi7_TI#The_3-inch_compact_floppy_disk Sellam
