It's a "mint set medal". They put it in the vacant "sixth slot" of the cellophane wrappers sometime in the period pre-2000 when no $1 coins were being made (I forget the exact dates). Some were plastic; some were struck on 1 cent blanks.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis