Psion Series 5 USB keyboard
zedstarr.com
zedstarr.com
I bought a box of dead Psion 5/5mx parts from ebay and used RasmusB's matrix-to-USB adaptor to hook up the tiny 53-key keyboard. I did a similar thing a few years ago with an old Psion MC400 laptop (Cherry 60 key) keyboard using a Teensy LC micro-controller
Most of the case parts in the box of bits from eBay have some sort of plastics failure - hinges being the main ones, a couple look like they've shattered/smashed from being dropped/crushed. Can't be long before a 3D-printed alloy version of these old cases appears surely...?