The tiny image of Oklahoma stamped onto the coin is called a counterstamp. ALWAYS post mint, counterstamping is done most frequently by individuals with a hammer and a die stamp. As Dave pointed out above, there are millions of them with more images than most of us can imagine.
Just an aside, but an acquaintance of mine, who recovers and refines silver, stamps his silver bars with weight, purity, and his company logo. It is a laborious process to do with any degree of precision. After trying this myself in his shop, every time I see a counterstamped coin, I wonder just a bit why people do this. Just for a fleeting fraction of a second. Then the thought is gone.
An internet search including the terms "counterstamped" or "counterpunched" should produce several hits of use.
Time for more coffee.