I bought a Filco numpad today and discovered it would lock up after few minutes under Ubuntu when pressing the num lock key.
Lucky this system has PS/2 ports so I decided to try it with a passive USB to PS/2 converter I had lying around and worked fine, but for future proofing I then went and dug out a Bluecube PS/2 to USB and it works exactly the same as PS/2.
the = key now acts like a backspace and a the 00 key now is just a 0.
I had a Red ESC Filco key around the place so decided to swap it out and now ordered a Red FILCO key to replace the = key