The imperial Ducat of Charles IV coined after 1355. Unlike those of other European rulers, the Ducats of Charles IV were coined in only a small quantity due to the limited gold resources in the Jilove and Kasperske Hory gold ore mines. It is therefore a very precious Czech coin today. The obverse of the Ducat bears an authentic bust of the Bohemian king and Roman emperor Charles IV with the imperial insignia – the crown jewels.The Ducat, minted from almost pure gold, was the highest coin of the Gothic period and mostly served as legal tender only in international trade. Paradoxically, the quality of the Prague Groschen was declining in spite of the immense economic and political rise of Bohemia. The content of silver in the Groschen decreased to mere 75% by the end of the reign of Charles IV, while the first Prague Groschens contained about 93% silver when first introduced in 1300.