Pull the panel backwards as you would expect (can take a lot of force tho) then when the "hooks" release pull upwards.
The side-panels are most likely hooked to the chassis at the bottom which causes a lot of friction.
Usually you can wear some rubbery gloves and whack it backwards.
But it that fails you can try and carefully pry it with something.
Many of these cases end up getting all bent at the rear for obvious reasons =)

Great case btw, the removable HDD cages makes for a really easy installation and was a big sellingpoint.

Got exactly the same case. Remove the 1 screw at the back and then pull it slightly back and then up. Not really easy to open indeed. Maybe rubber gloves as suggested above makes it a little easier.

Pic of mine, not identical but should help OP:

Thanks for the info! Don’t have rubber gloves but I’ll get a pair tomorrow. With bare hands, there’s no way I can pull or whack the cover backwards.
Also, I can’t remove the screw. You can loosen it but at some point it becomes stuck.
I carefully tried to pry it open but it just won’t move and I’m sure it will all bend up like bofh.fromhell mentioned.

Rubber gloves was just an example to help getting a bit better friction =)
I guess you could also use a strong tape (like duct tape) to make a handle so you can use a foot or something to really heave at it.
Also you could smack it with a rubber mallet around the hooked edges to hopefully crack whatever it is holding it together.
Who knows with old stuff, could just be the case paint sticking together like glue or someone spilled something sugary on it decades ago =)

bofh.fromhell wrote on 2023-04-24, 15:16:

Great case btw, the removable HDD cages makes for a really easy installation and was a big sellingpoint.

The thing under 3.5" floppy is a 3.5" tape drive for backups.

kixs wrote on 2023-04-24, 16:29:

bofh.fromhell wrote on 2023-04-24, 15:16:

Great case btw, the removable HDD cages makes for a really easy installation and was a big sellingpoint.

The thing under 3.5" floppy is a 3.5" tape drive for backups.

Yea but there's an easy removable HDD cage inside it.
Also the front 3.5" cage is easily removable (tool less IIRC) making it a nice case to build in.
Assuming ofc. that OP's case is what I think it is inside =)

A thread here showing the insides.
Tho this one is missing the nice HDD cage that goes under the PSU:
[vid+pics] My Brick 486 computer

Adding pics to clarify (A tad OT sorry OP =):

And as an added bonus, it seems I found my Intel Endeavor.

Kouwes wrote on 2023-04-24, 16:19:

Thanks for the info! Don’t have rubber gloves but I’ll get a pair tomorrow. With bare hands, there’s no way I can pull or whack the cover backwards.
Also, I can’t remove the screw. You can loosen it but at some point it becomes stuck.
I carefully tried to pry it open but it just won’t move and I’m sure it will all bend up like bofh.fromhell mentioned.

For my case I really need to remove the screw completely. If it's in (even loose) I can't remove the top.

My methods are approaching from the back, pulling with my 4 fingers on both sides and pressing my thumbs against the back of the case. You might still need some extra friction, but not as much.

You can also use a large flat head screwdriver on the back, maybe with something like a plastic card or thick paper to avoid damage to the painting.

I usually have more trouble putting them back than taking them off.

i stick a flat head in the slight gap on either side and twist gently to pry it a bit. the lower edge can get crusty in some environments, leading to corrosion and its a realllllly tight fit.

as for the screw, pliers, a bit of cloth/paper towel/etc, wrapped around it, rotate and pull a bit, should eventually come out. and it has to, to remove the shell. they aren't captive, but might be partially stripped. maybe combined with the flat head it might come loose.

There is some (minimal) movement but I still couldn’t get it off. As for the one single screw, I’ll just try and use force to get it out. I’m not sure why it has a little spring. Pretty weird construction, this case.

I’m not sure if it’s a good idea to use this case for a 486 build with my soundscape elite or gus classic. The whacking can’t be healthy for an old card, especially a long one like the elite

Kouwes wrote on 2023-04-25, 04:24:

There is some (minimal) movement but I still couldn’t get it off. As for the one single screw, I’ll just try and use force to get it out. I’m not sure why it has a little spring. Pretty weird construction, this case.

I’m not sure if it’s a good idea to use this case for a 486 build with my soundscape elite or gus classic. The whacking can’t be healthy for an old card, especially a long one like the elite

May not be the same with yours, but the ones I've seen like that have the thumbscrew captive with the cover - the spring is there to ensure its fully disengaged from the internal thread lug when removing. If so then perhaps the cover is just jammed on - try heating the obvious pinch points with a hairdryer to encourage some expansion.

Got it! Check out the pics - you need to push the cover up and then back. Definitely needs gloves.
Not the best case construction but hey, AT cases are hard to find these days.
Thanks again for the great help, much appreciated!!

Pictures…

Congratulations =)
Any hints on why it was stuck?
Also it seems you are missing the HDD cage =/

i've noticed that any of this style that were used for p2/3 systems (slot1, mostly), didn't tend to have the cage under the psu very often, since it tended to hit the cpu/cooler.

much suck

bofh.fromhell wrote on 2023-04-25, 14:51:

Congratulations =)
Any hints on why it was stuck?
Also it seems you are missing the HDD cage =/

It wasn’t really stuck. I just didn’t know you had to push it upwards.
The missing cage doesn’t really bother me. The case is in very good condition and I’m pretty happy with it!
I’ll post some pictures when I’m done with the build. Will be a 486 with a 5x86-133 cpu, pci graphics card (not sure, ET4000 or S3 Virge) and a gravis ultrasound. Running dos 6.22, only for games that actually support the GUS.