I reckon it might have one of those 386/486 boards, with VLB, soldered down AMD DX40, empty 486 socket.

Ooh, awesome. I have a 286 in that exact case.

I would guess you're going to end up with a 386SX-16, but I suppose it could be a DX, or even a later 486 era cheap 386, like a DX40.

Those ports on the back: the left one is a multi I/O card, with integrated gameport and parallel port, and the two male D-subs are not a card, but breakouts for the two serial connectors on that card.

It's obviously an AT motherboard, given the keyboard connector.

The 3.5 inch floppy drive in the 5.25 inch bay instead of its dedicated 3.5 inch bay that's right there for the taking could indicate that there is a 3.5 inch hard drive taking up the floppy bay, and there is thus an IDE card in the system, or perhaps it is indeed a later 386 or 486 motherboard with integrated IDE - but in that case it wouldn't make sense to have the multi-IO card, as the IO would also probably be integrated into such a motherboard.

And now that I look at it, there are no portless ISA cards in the system. Every other slot is taken up with an indented bracket that could not be a card.

Based on that I think the multi-IO card has IDE on it as well, and there is probably an IDE HDD in the 3.5 inch bay.

In fact, I think you will find a chip labeled "M5105" on that board!

The VGA card lacks DIP switches, so it's probably a later one. Oak or something. That might lend weight to either the 386SX or the cheap 486 era board theories, as this could have been a 386SX system that originally had an EGA card and was upgraded to VGA.

I should complete my guess I guess.. so 120MB Seagate ATA, 4x1MB SIMMs, Trident 9440 VLB VGA with 1MB.

My guess is it’s a 386SX-16 with 2MB, a 256k VGA (maybe a TVGA9000c) and a 40-ish MB IDE like a CP3000 or a ST157A. Battery leaked.

Seems very office and budget level. I'd say it's a late 386 era system (can be IBM/Cyrix 486 or just "386"). Around this time, most likely 386DX-ish. It could have an unusually low amount RAM (under 4MB) if it really was never opened to put to use and not going to be more than 4MB. As a 386 class, it likely doesn't have VLB. The only hope is that the VGA card being placed far down the slots where VLB is might mean it does have VLB, but it also could just be where there is enough room for a longer ISA card. 512KB Trident SVGA is my guess being a later era. 120MB IDE HD is a good guess too. Hopefully it still boots...

The fact that other people reported having a 286 system in the same case and that the model name might be "386slp" including the letter "S" as in "SX" and no clock speed indication makes me join the 386SX-16 camp. Further guessed specs: 2MB RAM, 40MB hard drive, low-end VGA, possibly Paradise PVGA1 or OAK 037C. Might be 512K, but might also be just 256K. I guess the system is too old for a Trident 9000, so a cheap Trident would be the ancient Trident 8800 (that's not a typo for 8900, but the previous generation).

The mainboard is likely going to have a 286/386sx chipset like the C&T SCAT ("single-chip AT") or the VLSI TOPCAT chipset.

Nice box 😀

The VGA card is the best hint. If this had been an early 386, it would have had a 9p digital output as well. No sign of that, which suggests this is a late 386 from the time when they were low-end. The 3x 5.25" and vertical 3.5" also points in that direction. So I'd say Am386DX-40. Pair that with a low-cost small baby-AT motherboard with single-chip chipset. 16b ISA multi-I/O card (with the extension bracket for 2x serial from a different card...) and VGA... something low-end. Oak or Trident probably, although C&T or UMC might also be options. 4x 1MB 30p SIMMs.