Clad specimens show slight toning. 4 blackened stainless-steel staples found affixed to each of three cardboard flips holding specimen each; each flip marked "Toned" I read somewhere that gaseous compound(s) containing sulfur can make stainless steel blacken... Thoughts?
Sulfur is not a gas. However, hydrogen sulfide gas found naturally in the atmosphere will tone coins and apparently, staples. The circumstances which you have described do not lead me to automatically think AT. Instead, it sounds like improper storage which would affect both the coin and the staples.
That's what I meant, some sort of gaseous corrosive compound containing thereof ... Must be some rather unusual levels of hydrogen sulfide... considering the specimens are only 30+ yrs old
Not necessarily. There are so many variables involved when it comes to coins toning that you will never be able to fix it on 1 thing. That's because every variable causes a different reaction with all of the other variables.
