yep, this is earthquake country they tell me. I laughed a little when I moved here from Kansas and they told me about it, then I got to reading up on the New Madrid fault and it wasn't so funny afterall.
At the end of the psr document it is dated April 21, 1997, but it is a Rev A version so the software probably came out a few months before that. Something else interesting that helps to date it, they give instructions for downloading technical information and instead of a web address to do the downloading they list a phone number, meaning it was a dialup BBS that they were running, so this was pre-internet for them, which got real popular in the mid-to-late 1990's. (just for grins I called the 800 number, it now belongs to ADT home security).
Sorry I'm not knowledgeable enough to help on the question about the security key. But it sounds like the security Privilege key is simply the key that unlocks the mpu board tray for removal from its card cage or compartment. That lock probably has some wires going to a switch that the lock activates. There is an UNLOCKED position and a LOCKED position to the lock. The psr instructions read like you should start with the mpu tray lock in the UNLOCKED position, then press the TEST button and then turn the mpu tray lock key CW to the LOCKED position to access the Privileged menu options. If your machine does not have the lock on the mpu tray then you'd need to install one or rig some way to touch the wires that the mpu tray lock switch would connect.
Maybe there's an old
geezer around here somewhere that's done this.