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,
Major thirds tuning improvisation. In contrast, chords cannot be shifted around the fretboard in standard tuning, which requires four chord-shapes for the major chords: There are separate fingerings for chords having root notes on one of the four strings three–six. The repetition of the major-thirds tuning enables notes and chords to be raised one octave by being "vertically" shifted by three strings. Notes and chords may be shifted "diagonally" in major-thirds tuning, by combining a vertical shift of one string with a horizontal shift of four frets: "Like all regular tunings, chords in the major third tuning can be moved across the fretboard