I can't really help you but it appears to come from some branded desktop computer, using a riser for the cards and having the keyboard connector on the front of the case. The keyboard connector especially might help you identifying the computer, if I'm correct about it. Also unless the photo is misleading it looks like a relatively small case.

bearking wrote on 2020-12-04, 09:39:

I'm asking for help, again, to identify this 286 mainboard. I've searched the TH99 and UH19 databases, but with no luck so far.. […]
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I'm asking for help, again, to identify this 286 mainboard. I've searched the TH99 and UH19 databases, but with no luck so far...

Apart from the AT keyboard connector, it has one parallel, two serial and one 9 pin video(CGA, EGA,???) connector.
So, any of you recognizes this board, I will very much appreciate it.
Thanks alot!

W86855AF is an Hercules compatible video chip: http://www.vgamuseum.info/index.php/component … inbond-w86855af ,likely a monochrome display is needed.

As for the board itself, if you could dump the ROM images of the two BIOS chips, that could help a lot for identification.

Keep in mind, TH99 is not the holy grail of x86 boards (which UH19 is based on), there are still a whole lot of boards never documented (this could be one of them).

Iam guessing that your motherboard is a LPX formfactor. Could be from a OEM classic machine.

Definitely OEM. Not too sure about LPX, the motherboard has a bracket like expansion cards have for some reason and the keyboard connector is at the front