Do you have access to Maint2?
If so you can make a backup, change the passcode, make a backup and compare.
If no access to maint2 you will need to search for 4 specific Bytes. Use procedure above on a lab system to determine the 4 byte sequence for passcode 1000 and search for same on the floppy disks (sorry can't tell you A or B)
It will be there in my experience as there appear to be 6 consecutive groupings for each side (Maint and CDE) I've only been able to change 5. My assumption is there is some magical "GOD" user name with passcode 1000. (as yet undetermined) You can use your lab system to determine their relative placement and modify the installer level.
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Occam's Razor - All things being equal, the simplest solution is the right one.