1992-d with Glue on Reverse

[car10]

While searching circulated cents I've come across quite a few 1992-d cents with hardened glue on the reverse. It's as if these were used in some kind of promotion at one time.

Has anyone else noticed these?

I'm just curious, does anynone know the nature of the promotion these were originally used in?

[OCD]

I don't remember what it was for but I have a 92D and a 94D that were used for promotions. Kept them for some reason. I've gotten a few nickels and dimes in the last couple of months. The dimes were for the March of Dimes, don't remember what the nickels were for.