I recently picked up a Numeridex 7000C2 keyboard. I haven't been able to find out much about the system it came with. The date code is 249-8219 so maybe 19th week of 1982?
It turned out to be an Oak Full Travel Membrane board:
When I tested the matrix it turned out that a number of keys didn't work properly so I decided to take it fully apart, clean it and see if I could reassemble it and get it working.
The switched are held directly to the metal plate by melted plastic rivets through the keyboard membrane. I used a wood chisel to cut off the rivet heads and remove the switches and the membrane.
A plunger presses a central spring against the membrane to active the switches.
The Shift Lock and Caps Lock are latching switches:
The membrane parts are glued together so I did not attempt to separate them. When I tested the membrane out of the board, however, all the switches were working. After cleaning the membrane, switches and springs, I began to reassemble the board. I used clear silicone sealant (same as used as an aquarium sealant) to hold the switch pegs in the plate. I chose this because I found it held the switches firmly enough, but still allows for removal of the switches and easily cleans off plastic.
To connect the membrane I used trio-mate 17pos connectors, breadboard pins and prototype board:
Wired up the Teensy:
Then reassembled the case. I did touch up the case with sage green spray paint which matched quite well. I haven't done the edges of the black front plate yet though.
This is the matrix I came up with:
The switches are linear, rather heavy and and overall I would say very "meh." It was still worthwhile imo, however, since I had never had the chance to try these switches before and it did make for a fun little project.
Quick video of banging away on board: