what is this switch type?

[Volny]

I bought these 'stemless' switches the other day. I was so excited to finally see a switch that would allow a central legend to be backlit without obstruction from the + stem, that I snapped them up without paying too much attention to their specs. I assumed that the circle in the stem would hold a regular MX keycap (from the outside by hugging the cylinder, not from the inside cross as is usually the case). Though I was wrong about that.

It turns out that not only do the switches not work with regular keycaps, but they have an unusual pin placement that doesn't fit with any keyboard PCB I've seen either. I can't actually see any info on the aliexpress page about what type of keyboard/keycaps they're compatible with. Though I'm kind of curious about what these things actually are. Does anybody know?

[Findecanor]

It looks like it could be Kailh PG1593 series.

Azio retro range keyboards have a variant with translucent slider and upper housing. Their keycap mount looks the same. The pinout looks similar to other Kailh switches with centred LED.

Is there no marking on the switch housing?

[Suds]

Das Keyboard uses an Omron-made version of these in some of their keyboards. Doesn't look like it's pin-compatible with the Kailhs though.

[Findecanor]

Das Keyboard uses an Omron-made version of these in some of their keyboards. Doesn't look like it's pin-compatible with the Kailhs though.

They are a bit similar in that they are both mechanical switches with the slider around the LED, but they are quite different in other ways.
You can see the innards of the Omrorn switch here.

Steelseries uses a lower-profile version of the Kailh switch they call Steelseries QS1. Like the Kailh switch in the top post, the slider and LED are not entirely centred. The contact mechanism works on the same principles as Cherry MX.

[Volny]

It looks like it could be Kailh PG1593 series.

Azio retro range keyboards have a variant with translucent slider and upper housing. Their keycap mount looks the same. The pinout looks similar to other Kailh switches with centred LED.

Is there no marking on the switch housing?

OK, so gathering by that link (and the Anandtech article it links to), they're called "Typelit" switches, and are likely heavily inspired by Omron's Romer G switches. And it seems like it may have actually been made specially for this gaudy Azio thing. It's kind of ironic that a switch with such a modern feature as full top-to-bottom backlighting only exists for the sake of a "retro" board, to mimic a board from a time when LED backlighting wasn't even possible.

Well, I find that disappointing all round, but thanks for helping to solve the mystery! 

BTW, there's no marking on the switch other than "Kaihl" on the top, and a single "F" on the bottom.