Yeah every disk I've had sent from the US have been perfect. Wondering if it's humidity or temperature or something?
Last bits I got from the US was SimCity original boxed and IBM PC DOS 2.10 (both disks). Sealed disks, normally blank disks, that I've got locally have been great though.
I did do some testing on kiwi-moulded disks, I know tez has too, and you can actually clean them if they're valuable enough.
I cheated a bit for my testing and just used an isopropyl wipe through the drive window - it worked but I missed a spot (curses). Wasn't a valuable disk, just wanted to try it
Also tried swapping the donut between disk cases and that worked out quite well - haven't used that technique to revive any rare OEM disks yet but the trial went well.
Is your AT a genuine IBM? If so, congrats
Let me know if you need anything, I've got quite a few spares stacked up at the moment.
Still need to order a PC-AT case, have been putting that off as my wallet has been scared.