This is pretty fun

The winner of this session will receive a small collection of Lincoln Cents. All 9 coins are from the Denver Mint. You will receive the 1973D through 1981D. They will be in 2x2 plastic flips. And as you all should know, 1981 was the last year copper was used in U.S. Pennies. O.K, now for the question, which has two parts. You must get both parts right.

What was the smallest monetary unit issued by the United States?

And from which date, to which date were they issued?

I will draw the winner at random from correct responses on Wednesday evening, May 16th. Good luck, and have fun!