this is the back of the keyboard and exhibits engineering
design of something built to last. there is no mechanical nor electrical
contact between the keys and the circuit (click image for close-up).
operation is by reed proximity switches (the glass tubes). inside
sealed glass tubes, two small contacts connect in the presence of a
magnetic field. the keys themselves have a small magnet on the ends their
travel which trigger the reed relays.
interestingly, when i acquired the machine the key travel was somewhat
stiff with age, but fully functional. i lubricated the keys using
precision teflon grease (not oil!) and they were soon restored to their
original tactile lightweight response.