Got this keyboard some months ago for cheap. After looking around and not being able to source the protocol for it I decided to USB convert it with an RP2040 and QMK. It uses linear Matsushita Spring Over membrane switches. The actuation occurs at ~80g with bottom out at ~100g. Their actuation point occurs at about 2mm with a total key travel of 4mm.
I'm actually not entirely sure to what system this belongs as it has some unique features that I was unable to find in known Panasonic Word Processors from the 80's - 90's. I've associated it with the KX-W1525 as its the closest match I was able to find (based on design, age and color scheme).
Gallery/Conversion: https://imgur.com/gallery/tas5SIi