Sadly there are a couple of very light marks on the brown disc surface – MODS. 

Disc Game for Atari ST Computers. 

MODS: The condition of 3.5 Inch disc surfaces is becoming an issue in the 16-bit collecting scene. Nobody expected people to still be booting these games up thirty years later, and, depending on how they've been stored, it is common to find small discolouration patches, white spots, and even mould on the brown surface of the disc. We have had some limited success cleaning light spots from disc surfaces in the past. Some people clean floppy discs with an alcohol solution, or bathe the disc in soapy water, but this depends on the marks, and can still render a disc unusable. We won't list games with big mould patches, but games we list with MODS will have a light issue - perhaps only on one of multiple discs - perhaps light enough to still play through, or be gently cleaned, but these games are sold as untested for parts only.