Hold your scrot up to a bright light, ask someone if they can see any light show through it where it turned clear.  I'd make a joke about pin-pricks of light, but that would be carrying things a bit far.

what about floppy rot ? i have a bunch of old DOS games that i am freaked out about now.

Whenever I buy used cd's, I hold them up to the light. I have seen holes before, but always assumed it was due to mishandling. I've heard CD-R's degrade over time, and have seen some discoloring/audio warping on a few that were left in the car for years. Other than that, I'm clueless. I would like to know more about it.

64DD wouldn't get disc rot, it would get bit rot, since the DD disks weren't optical discs.

Yeah, Discs are supposed to generally have a life span of 25 or so years than they start corrupting themselves or something, this also has to do with sunlight, moisture, and other variables. This is one of the reasons I don't bother collecting for Disc based consoles because in addition to moving parts and finicky lasers you have fragile rotting discs to worry about (and those crappy jewel cases). This is also why I stand 100% disc drive replacement flash solutions for consoles.

On another note the brand of disc probably influences the rate of rotting, discs made specifically for archival purposes probably last longer, but they cost more so I doubt anyone in the game business used them. Supposedly the best solution to bit rod are "M-Discs" they have some kind of silica(rock) on them that's in theory supposed to last a super long time.

Yeah, all magnetic media will suffer bit rot over time as the magnetic medium loses strength. IIRC, collectors of old 80s DOS games accept that the 5.25 floppies may be dead and base the value on the completeness and condition of the packaging materials.

I've seen discs that have the pits in them, but they've all been improperly cared for. I've never seen pits on discs that have been treated well. This isn't a guarantee, or even good science, just my anecdotal experience. I'm curious if anyone has seen pits on discs that otherwise should have been mint.

Are they dead or just blank? I'm curious if the magnetic medium could be restored, i.e. re-write the discs.