PSIBER stood for "PostScript Interactive Bug Eradication Routines".
The author seems to have used it to debug an application called the PseudoScientific Visualizer which was used to make some maps of the 80s Internet and some kind of adventure game.
I found some lovely, vintage 1994, html documenting the whole system with much better images:
Brought one into Illustrator and Merveilled it:
It's fascinating that Safari opened the PostScript file in seconds, macOS Preview didn't even try, and Illustrator took a minute and a half to import it
Inkscape was totally copacetic and only needed a second or two.
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