The case of the Macintosh is yellowed, which is common for such an old computer. A good thing is that it's uniformly yellowed. There is no stains, dents or cracks of the case.
After opening the top cover the things don't look so encouraging.
The top cover is rusted and this is a bad sign in general...
...because there is also a lot of rust signs on the power supply and other metal parts.
There is a lot of dirt, rusty particles... and even spider webs.
The PRAM battery is dead (0.04 V), but it has not leaked - lucky me!
The floppy disk drive will need a special attention as well.
Neither good or bad... we will see...