Could someone please tell me what a 

LaserWriter IINTX upgrade kit is.

Its a small box, which has a bag inn it , seemingly
containing 6 chips (look like ROMS) and a IINTX manual.
The installation instructions are most informative and say, in full,
"This product must be installed by an Apple ........."

SO what does this do ? At first I thought it might be a NT to NTX
upgrade, but I thought that required an entirely new board.

Any info appreciated.