> Write-white?  Did the engineers own stock in a toner company or what?

Write-white just means that the drum has to be charged where it is NOT
going to attract toner particles.  Thus the laser is used to write the
white areas of the page.  But the toner is still black, and a write-white
laser printer won't use noticably more toner than a conventional
write-black printer.  In fact, it typically uses ever-so-slightly less.

The described LN01 printer is an OEM'd Xerox 2700.  Pretty good at
printing text, but it doesn't have bitmap capability, and the font
file format was undocumented, apparently because Xerox and/or DEC wanted
to make sure you paid $$$ for their fonts.  Apparently there was a later
LN01S model with a different RIP which could handle bitmaps.

I wasn't aware that the LN01 was a write-white printer, though it's
not especially surprising.