8 heller, Mainz, Gustav II Adolf, 1632
The city of Mainz, near Frankfurt in Germany, was in Swedish hands between 1631 and 1635. Both gold and silver coins were minted during this time.
The coin you see here has a low denomination of 8 heller, and it is what is known as a one-sided coin, stamped on only one side of the coin. G A R S is an abbreviation of Gustavus Adolphus Rex Sveciae – Gustaf Adolf, King of Sweden, and 8 indicates the denomination 8 heller.