German coins of the modern era can be divided into three categories: those minted by the German states prior to and immediately following the unification of those states into an empire in 1871; coins circulated between World Wars I and II; and the separate monetary systems that were established after 1949, when Germany was divided into eastern and western nations. The two countries reunified in 1990 and have used the Euro since 2002.
The coin of the realm for the German states was the vereinsthaler, which was worth 360 pfennig (the root word for the British penny), although this value varied from state to state. With unification came decimal coinage based on the mark (100 pfennig to the mark). This new coin, struck in silver or gold depending on its value, replaced the vereinsthaler, which was worth three marks—well into the 1930s three-mark coins were known as thalers.
Though not especially valuable, notable coins minted between the wars include those made out of aluminum, zinc, and iron, which was how the pre-Weimar Republic government coped with inflation. Marks became known as reichsmarks in 1924, and in the 1930s, German coins reflected the ascendancy of the Nazi state.
After the war, West Germany adopted the deutschemark as the foundation of its monetary system. The German Democratic Republic, or East Germany, also used the deutschemark and even called it that for a period, but these ostmarks, as they were known, never enjoyed the stability of their western cousins.