It's been a long time but 'psn' probably stands for 'Pigs in Space' - our internal code name for the project (Apple's code name 'Eagle' leaked, but ours never did). Given all that I'd guess that this is one of the early releases we gave to Apple that has somehow escaped - we used to fly to Oregon and copy disks to do releases to avoid California's sales taxes - UniSoft actually had an online modem based system where customers could log in and download the latest software - at the time CA tax law didn't explicitly cover electronic delivery of software, we were sued by the state and they lost setting a precedent However I can see the latish floppy bug fix (there was a hardware bug found in the FDB/ADB chip where if we accessed the floppy on only some systems the keyboard froze, turned out we were spinning reading the timer while reading the disk, doing it so fast the clock to the FDB chip sped up) and the older pre-fix code in 'sony.c.~8A' - that sort of places the release in time. Missing is all the auto config support (ability to add 3rd party drivers to the kernel in the field, something that at the time you usually couldn't do without source), fixes for large screen support, all my appletalk code is missing too. Yup I wrote a lot of that, I did all the console stuff (font renderer, vt100, mouse, keyboard, fdb/adb, ui event queue etc).