@dst, it might have come from one of those old blue Whitman folders as the coins sometimes were a bit loose in the holes and tape was a common way to ensure that they wouldn't fall out. Hopefully there isn't differential toning underneath that tape residue.
"If you climb a good tree, you get a push."
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz