I have an IMSAI IKB-1 keyboard. The IMSAI 8080 used in the movie actually would have used a terminal with it's own keyboard. I have one with a Lear Siegler terminal. The IMSAI IKB-1 keyboard came with the IMSAI PCS-80/30 computer (a later IMSAI computer) which I also own.
Here's the system it actually came with. You will notice my keyboard doesn't have the graphics. There were very few made and mine is an early one. The real keyboard used in the movie also didn't have a numeric keypad like those display photos show.
Here's the internal board front:
Here's the internal board back:
Here's a pic of the top of the key switch with the key cap removed along with the underside of the key cap (CTRL key):
When pressed, the plastic middle piece goes down and the two metal contacts come into contact and "clap". Hence the sound.
That's as close to taking it apart as I get. It's a rare keyboard... literally.
Love to hear what you guys and gals think. Haven't seen one of those key switches before personally .
Edit: Added last picture