Better keyboards than the model M were the old leaf spring and flyplate type used in the IBM 3742's and 5251's. These were amazing. When a key was depressed, a flat leaf spring would distort, forcing a fly plate up. The fly plate was plastic which acted as a dielectric. Therefore relaxation oscillator would change frequency between when the fly plate was hovering over two PCB pads, compared to when it was up. The encoding scheme was EBCDIC, not ASCII. The clicking was made by a separate solenoid and plunger that hit a metal plate. One solenoid for the entire keyboard. The tactile feel and click sound were wonderful.
In my first job at IBM in the city of Melbourne, occasionally I used to go out on site and fix the individual keys in a keyboard. I was well paid, but the keyboards were so expensive, it made economic sense to fix them. After tens of millions of key strokes, sometimes a leaf spring would fracture. It took a lot of patience to hook a fly plate to the leaf spring. Sometimes it would take 20 minutes just to reassemble one key. Even though the keyboards had a protective membrane, smoke particles from cigarette addicts would affect key registration. The fix was to CAREFULLY remove the PCB, clean it with isopropyl alcohol and CAREFULLY reassemble it. With the 3741's and 3742's, I often found money in the keyboard area.
IBM also made some interesting keyboards for their 129 and 029 card punches. Some used ingenious diode matrixes to encode a keypress.
Today I develop electronics for satellite communications. I don't know why but those days were a lot more fun for some reason. Maybe it is because the keypunch operators were often pretty women who were well dressed. These days I work with nerds and geeks.