using a standard design for the reverses (the , the eagle insignia of the German Empire) with a design specific to the state on the obverse, generally a portrait of the monarch of the kingdom or duchy (and not that of the emperor); while the free cities of Bremen, Hamburg, and Lübeck each used the city's coat of arms. Occasionally commemorative coins were minted, in which cases the obverse and (much more rarely) the reverse designs might depart from the usual pictorial standards. Many of the smaller states issued coins in very small numbers. Also, in general all states' coinage became very limited after the First World War began. Well-preserved examples of such low-mintage coins can be rare and valuable. The Principality of Lippe was the only state not to issue any gold coins in this period. Base metal coins 1 pfennig (copper: 1873–1916, aluminium: 1916–1918) 2 pfennig (copper: 1873–1916) 5 pfennig (cupro-nickel: 1873–1915, iron: 1915–1922) 10 pfennig (cupro-nickel: 1873–1916, iron and zinc: 1915–1922) 20 pfennig (cupro-nickel, 1887–1892) 25 pfennig (nickel, 1909–1912) Silver coins Subsidiary silver coins were minted in .900 fineness to a standard of 5 grams silver per mark. Production of 2 and 5 mark coins ceased in 1915 while 1-mark coins continued to be issued until 1916. A few 3 mark coins were minted until 1918, and mark coins continued to be issued in silver until 1919. 20 pfennig, 1.1111 g (1 g silver), only until 1878 mark or 50 pfennig, 2.7778 g (2.5 g silver) 1 mark, 5.5555 g (5 g silver) 2 mark, 11.1111 g (10 g silver) 3 mark, 16.6667 g (15 g silver), from 1908 onwards 5 mark, 27.7778 g (25 g silver) These silver coins are token or subsidiary currency for the gold mark and are therefore legal tender only up to 20 marks. However, all silver 3-mark s issued before 1871 enjoyed unlimited legal tender status even after the switch-over to the gold standard. This ended with the demonetization of the in 1908 and the introduction of the new subsidiary 3-mark coins. The 5-mark coin, however, was significantly closer in value to older thalers (and other such crown-sized coins). Gold coins Gold coins were minted in .900 fineness to a standard of 2790 mark = 1 kilogram of gold (a mark was therefore about 0.3584 g of gold). Gold coin production ceased in 1915. 5-mark gold coins were minted only in