I know that GameStation used to provide a CD-ROM and DVD polishing service to remove scratches and restore them to as good as new.
But this is a CD-R and I suspect that exposure to sunlight may have erased some of the recorded data, or at least made it more difficult to read, thus I suspect that method may not be applicable in this case.
Edit: There aren't any visible scratches on the disc surface anyway.
However, the previous owner of the Catweasel card said that he had bought it from a second-hand (charity) shop, and I'm thinking they had displayed it in the window, and that's what caused the deterioration. And I used drivers I had downloaded to test the card after I received it, so I had no cause to use the CD-R at that time.
Now, I am just trying to recover the files purely for preservation purposes.