Have you tried finding your board in Total Hardware 99?
It's quite a search but perhaps you can find it there, it has tons of manuals for older components like your board.

Are there any readable marking on the board that may help identify your board?

Perhaps the "PCI" bit in the middle will help, could you perhaps take a closer picture of it?

Edit: You could try looking here and here

Well, I did some looking around and this one looks quite similar: http://artofhacking.com/th99/m/A-B/33238.htm
Does this one look like yours?

Thanks for the reply.
Well, it has Terminator written in some corners and RT-423X written between the second and the third ISA slots. I can post a better photo latter, this one was made by the seller. I searched for these keywords everywhere, only thing I found, was in this forum: http://www.winhistory-forum.net/showthread.ph … id=4101&page=11 The guy seems to have the same problem as I do. I registered there, but never got an email confirmation (the post is very old anyway), and Google translate wasn't helping that much. I will take a better look at Total Hardware 99.