That I/O shield is a proprietary one from some manufacturer. The hole pattern is typical for early ATX, it was the standard for about five minutes. The back of that case has screw holes for an I/O plate; cases from that era typically came with an I/O plate with that pattern held in place with screws, and at that time most motherboards worked so you didn't have to bother to change it. Here's an Ebay listing for one that should work: https://www.ebay.com/itm/186385791379?itmmeta … VgAAOSw8HxmFp0q

Repo Man11 is probably right. For a short period non-disposable I/O shields were coming with the case and used their own way of mounting. Maybe that's what you've got here, minus the matching case.

Thanks very much for the information!

I found a spare I/O shield in my spare parts that matches (with a few extra/empty ports). I might pickup that one you mentioned though but we'll see.

Here is an example of the stock I/O plate that many cases came with. Since most motherboards the time fit this, it was left in place and the I/O plate that came with the motherboard was left in the box (and eventually thrown away). Then the computer was upgraded and the motherboard was pulled and now had no I/O plate.

The other image is an OEM plate that did fit in a standard case - if you look closely you can see that it had to be put in place from the outside of the case rather than inserted from the inside like a standard I/O plate.

Interesting and thanks again! I'm using something like the bottom picture (ie. motherboard doesn't have gameport or built-in sound) but it's working.

Maybe someday I'll find a panel like the first one you listed (but with gameport/sound blocked).

Thanks again! 😀

Synchronicity: on my local Craigslist there is a P2 system for sale in a desktop case that appears to have a nearly identical I/O plate to what you have. You can see how the two tabs are to fit in slots in the case.