Pitted Cases?

I’m constantly scouring the web for my next vintage find, and occasionally I come across cases which exhibit pitting, like this 1960s Longines I saw on eBay today. Just curious if this reflects a manufacturing defect, or some type of very rough or unusual treatment over the years. Any metallurgy types care to chime in?

Like this one of mine....

Any treatment, cure, advice, Archer?

And we have a winner

Found this on pitting of stainless steel
"Localized corrosion such as pitting and crevice corrosion of stainless steels generally occurs in the presence of halide ions, typically chloride (e.g. coastal and deicing chloride salts - sodium, calcium or magnesium chlorides; hydrochloric acid; bleach - sodium or calcium hypochlorite; and other chloride compounds). "

Human sweat normally contains

• Sodium (0.9 gram/liter)
• Potassium (0.2 g/l)
• Calcium (0.015 g/l)
• Magnesium (0.0013 g/l)

So you have three possible culprits present in sweat.

Sweat can also contain Ammonia if a medical condition prevents proper processing of proteins.
Sweat can also carry other chemical contaminants out of the body.

I suppose sea water or salt air in some locations can be as corrosive.