Buckling spring IBM model M2 $29 on Ebay

[Tactile]

These are the terminal version with a phone plug connector and are easily converted to PS/2 or wire it to a Teensy with TMK or Soarer's converter for USB.

There's more info about this model here.

[ed_avis]

Now $10

[Touch_It]

Half tempted.  If in good shape, these are quite pleasant to type on in my opinion.

[elecplus]

Would you rather have one tested and working?

[romevi]

Interesting. So mechanical?

[elecplus]

Yes, they have buckling springs. But the caps, controllers, cases, etc. are NOT interchangeable with the Model Ms. And the build quality is very unimpressive.

[chyros]

Especially the capacitors, which are notorious for failing. ALWAYS get these tested before you buy.

[Touch_It]

Would you rather have one tested and working?

Yep.  Things are evil to work on.  plastic key stabilizers, and plastic clips on the inside are easy to break.  Along with what Chyros said, they are not great keyboards if you have to work on them. 

Saw you had one tested working for $25 Cindy.  A good get if these are your thing.  To me they feel half way between Model M and Model F keyboards. 

[elecplus]

I have some for parts/repair too. I have so many interesting keyboards, I don't really want to spend the time to fix these!