Can you tell me what kind of keyboard is this?

[ksm123]

I've found this keyboard on my attic, It was part of 286 system my friend gave me. I got this keyboard with numpad "*" stem broken and without keycap.
It used to use AT connector, but I switched cable to PS/2



Switches are terrible, there is no internal spring in the switch.
Without keycap once you press switch it stays down.
Switch action feels scratchy, there is a lot of friction. Spring is two weak, return action is nowhere near as fast as MX Blue.
There is audible click on key press, switch actuates about half way through.

1x1 keycaps are interchangeable with Cherry MX keycaps (tested with my Black Widow).

As requested below, labels on the back:
1) Prosystem Computer Technic passed quality control
2) K-450 S/N 0054068

[esoomenona]

Label on back?

[fohat.digs]

I think I had one of those. Is it NMB maybe?

Good keycaps but domes and plungers, if I remember.

[Tarzan]

According to a bit of directed Googling, it appears to be a Copam K450. 

http://toronto.canadianlisted.com/computers/mechanical-keyboards-2-copam-model-k-450-richmond-hill_2480867.html

This model would probably be a hybrid membrane type, some other Copam models were said to use Cherry Blues or Blacks, which may explain the stem.  The plunger/stem compresses two layers of plastic (?) to make a switch connection, but the spring is only the one under the keycap.

GH link to older discussion: http://geekhack.org/index.php?topic=15353.msg296723#msg296723

Don't know if they are repairable, if the one switch is broken you could try to extract it from the backing plate, but it would probably take a donor board to find suitable replacement parts.

[simon_C]

Yank it apart and put the doubleshots up for sale, and while youre in there take a look at how the switch works.

[ksm123]

Thank you very much.

I've suspected this keyboard is worthless.

I'll keep it as keycaps donor for ErgoDox I see in my future ;-)

[son]

According to a bit of directed Googling, it appears to be a Copam K450. 

http://toronto.canadianlisted.com/computers/mechanical-keyboards-2-copam-model-k-450-richmond-hill_2480867.html

This model would probably be a hybrid membrane type, some other Copam models were said to use Cherry Blues or Blacks, which may explain the stem.  The plunger/stem compresses two layers of plastic (?) to make a switch connection, but the spring is only the one under the keycap.

GH link to older discussion: https://geekhack.org/index.php?topic=15353.msg296723#msg296723

Don't know if they are repairable, if the one switch is broken you could try to extract it from the backing plate, but it would probably take a donor board to find suitable replacement parts.

Bit of a necro here, but I've got the Copam K-452 - seems to be about the same as the K-450. Looks the same, anyway, and the PCBs inside mention the K-450. The pictures in that older thread are gone, but this is what the K-452 switches look like inside:



The bigger spring sits under the cap to keep it up, the white plastic attaches to and moves with the cap, the green bit makes contact with the membrane sheet, and the smaller spring, which goes between the green and the white thing, allows the green bit some give. The click leaf does what it's supposed to.

Not all of the caps are doubleshot, by the way - at least not on my keyboard. Seems a bit random, even, even though all the keys appear to be original. Some caps look like they were meant to be printed doubleshot but instead had the same color plastic molded in, then printed by some other method that left a raised surface.

[False_Dmitry_II]

Seems overly complex.

[hwood34]

Seems overly complex.

Or on par with an MX blue