Time to make some room.
This is a complete tested working Northgate with a yellowed case and keys. Besides the color, there are not any other problems.
I removed the original switches and replaced them with Matias quiet clicks and the board probably does not have more than a few hours use on it since. I was 2 switches short, so I used the originals for Num Lock and Caps Lock, partly because I wanted a sound to remind me that they had been pressed (if accidentally).
The original keyboard had seen some real use, the keys have a fair bit of shine (especially the space bar) and the yellowing is uneven, but they are doubleshot caps (in colors for some) and so the legends are still full. I am not that good with Retro-brite but I suspect that it could all be brightened up considerably by someone who knows what he is doing.
I cleaned and painted the metal plate, and replaced all the wire stabilizer tabs and lubed the stabilizers.
$45 shipped domestic US.
I have some other Omnikey 101 parts that I will ship free with the keyboard such as the original switches (in decent shape but well-used) for $15 and a PCB with several of the soldering pads up or off for $5 additional.