50 State Quarters to form what is known as a "mule". Only sixteen of these specimens, produced on dollar planchets, escaped from the mint. A 2005 Minnesota double die quarter, as well as a 2005 Minnesota quarter with extra trees (another die error), have both triggered numismatic interest. An unusual die break on some 2005 Kansas quarters created a humpback bison. Relatively more common are Kansas quarters bearing the motto "IN GOD WE RUST." The United States produces proof coinage in circulating base metal and, since 1992, in separately sold sets with the dimes, quarters, and half-dollars in silver. For the silver issues,
Quarters of Rome 1926. These two were later officially renamed, the XVII becoming "Trieste" in 1946 and the XVI becoming "Monte Sacro" in 1951. Other quarters have been renamed: the quarter XV, previously called Milvio, became "Della Vittoria" in 1935, while the III, once known as Vittorio Emanuele III in honor of the King of Italy, was renamed "Pinciano" in 1946. In 1961, 18 more quarters were established and numbered XVIII to XXXV. Some of the new quarters were created dismembering five eastern suburbs of the city, some others were established in the rural area around the city, the so called Agro Romano