Just a wild guess here, but perhaps intrusion detection.
Go in BIOS and see what the logs say. Try clearing them, then see if you get an intrusion detection flag set off when you restart the PC without the cover. Might also have to set BIOS to register (i.e. not ignore) intrusion detection for this, though. But again, this is just a wild guess on my end.

Yeah possible intrusion detect but most do not have that many wires...

Look up the system board and see what the description for that connector says. I found this site saying it might be a D983 but the connectors don't match up with yours.

edit: probably a d1085-a or -e. manual says "cover detection".

These 4 middle traces look like they are meant to be cut, for some sort of configuration maybe? Perhaps this wasn't meant to just touch a solid piece of metal that shorts everything together but rather there could be some piece of electronics connected? Some kind of plastic card with similar contacts? At least as an option, maybe it was never used that way but the design allowed for it. This would provide more than simple intrusion detection, it could be asset tracking, HDD data encryption, etc. Such card would be removed (preferably along with HDD) if the machine is to be scrapped obviously.

To me this looks like a smart card reader. Many models of Siemens-Nixdorf had a smart card reader, but from these pictures Ican't see the front cover of the computer, so I can't be sure

Bit more info, I've rechecked and that part does not in any way connect with the top cover . As to a Card reader, although there is a slot in the desktops right front pillar it must have been optional as its empty on the inside. I include a frontal picture. Normally there's a green sliding plate in the front but that was damaged so I removed it.

I'm going with intrusion detection as well, based on this Siemens Nixdorf System Board I found on The Retro Web.

https://theretroweb.com/motherboards/s/siemen … ard-d1127-a-b-c

Not the exact same board, but it has a very similar connector in the same general location marked as "Cover Monitoring".

Have you looked to see if your specific board in on The Retro Web? They have quite a few Siemens-Nixdorf boards on there. You may get lucky and it's on there already. If not, you can add it. 😀

https://theretroweb.com/motherboards/?manufac … 24&showImages=0