Well, after all, I was not lucky. All of the keyboards mentioned in my first post turned out to use rubber domes.
However, there were a couple of surprises.
Some initial impressions:
1) Alps AT101-102 is very mediocre, even for a rubber dome, but the keycaps are very good. They are thick, made of PBT, and both Latin and Cyrillic legends appear to be dye-subbed. I will definitely save them for future use.
2) The second keyboard is still a mystery, its manufacturer is unknown (maybe later I'll find some clues inside). My guess is that it uses sliders over rubber domes. The keycaps have a very distinctive shape. They are much higher at the bottom than at the top, and all their edges are very sharp. Like the front edge of my MacBook Pro. They are double-shot and appear to be Cherry MX-compatible.
3) The third keyboard (HQKRB-2001) is the biggest surprise of the bunch. It appears to be made by a Taiwanese company called Key Mouse Enterprise. It also uses sliders over rubber domes, but it's actually rather awesome to type on. I don't know how they did it, but the keys are very light, but with a pronounced tactile "bump." The return action is strong and swift and the keys emit a very satisfying "thud" as they return to their initial position. The keycaps are double-shot ABS and they appear identical to the keycaps shown here:
http://deskthority.net/photos-f62/click ... t4861.html They even use the same god-awful font for Russian legends (with letters З, Я, Ж and Б being especially ugly). The only difference is that they use Cherry MX mount instead of Alps mount.
However, the most distinctive feature of this keyboard is that it has a built-in speaker which beeps every time you press a key. As you can imagine, it gets annoying pretty quickly. One day I will open it up and rip the speaker out, because otherwise it's a very good keyboard to type on.
4) DEC RT-101+ uses NMB sliders over rubber domes. It's a good rubber dome board, but not as good as the previous one.
One of the sellers also decided to throw in some keyboards I didn't buy as a bonus. What I got is:
Chicony KB-5311 in dark. The case is dark blue, the alphanumerics are coffee brown and other keys are dark grey. It looks very handsome, too bad it's as mushy as mashed potatoes. No joy in typing on it.
BTC 5339R-O. As far as I understand, it uses some kind of linear capacitive switches. It feels like nothing I have ever seen before, with keys being very light and completely linear. The keys activate way before bottoming-out, so typing on this keyboard is a pleasant experience. It's not silent however, because all the springs under the keys strongly resonate when I'm typing at full speed. I also make a lot of typos on this keyboard because of its linearity. But it must be awesome for gaming. The keycaps, unfortunately, are of low quality (they are ABS and pad-printed, with many legends fading away and some completely gone).
BTC 5139. A mediocre rubber dome keyboard with Cherry MX-compatible keycaps.
IBM KB-9910. A good rubber dome board, I actually use one of them in my office. It's compact, it looks good and is almost completely silent. This copy turned out to be almost new, except for a swarm of dead cockroaches inside. (Ewwww...) BTW, the circuit board and the case are marked as "KB-7953", so I think this keyboard is identical to IBM KB-7953 which was made by Chicony.
Looks nice and clean!