Cast metal (likely aluminium) keyswitches! They have small microswitches inside of them, along with rubber gaskets (probably ultra extreme environments).
Going from the pins, likely hotswap as well.
![Image](https://farm5.staticflickr.com/4599/25305994098_ed258a3656_h.jpg)
![Image](https://farm5.staticflickr.com/4637/39170692841_b688f1958b_h.jpg)
![Image](https://farm5.staticflickr.com/4593/39143913822_217922aefd_h.jpg)
I have about a numpads worth of the switches with date codes (1981 to 1985):
- 8120
- 8126
- 8126
- 8126
- 8126
- 8126
- 8126
- 8127
- 8448
- 8501
![Laughing :lol:](./images/smilies/icon_lol.gif)
![Image](https://plot.ly/~haata/438.png)
![Image](https://plot.ly/~haata/440.png)
Album: https://www.flickr.com/gp/triplehaata/a8a2p5