Cross post from DTI recently picked up an ITT Courier keyboard that was used with the ITT Courier 1700 terminal, a competitor for the IBM 3178 in the early mid 80's. The keyboard is quite beefy at over 3 kg. It has cast upper and lower case halves. The switches are the interesting part. I am not familiar with them and was hoping someone could identify them. There is a Micro Switch sticker on the plate. The switches are very short and appear to sit on top of a single membrane, sandwiched between two plates. They are very tactile and have a solid metallic sound. After bending a few tabs to separate the metal plates, I discovered that it uses a diaphragm spring over membrane mechanism. The switch plunger acts on a coil spring, which acts on the diaphragm spring (similar to the beam spring). When the diaphragm buckles, it makes contact with the membrane sheet.
Here are some pics:
Here is a short video of the sound:
