The Silbergroschen was a coin used in Prussia and several other German Confederation states in northern Germany during the 19th century, worth one thirtieth of a Thaler.
The Silbergroschen was introduced in Prussia in 1821 and was later adopted by other states as they switched to using the Prussian currency system of 12 Pfennig = 1 Silbergroschen, 30 Silbergroschen = 1 Thaler (Vereinsthaler from 1857).
Silbergroschen were replaced with 10 Pfennig pieces when the German Empire decimalized following unification in 1871.
References
Silbergroschen Wikipedia(Text) CC BY-SA