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The first pocket watch was created in Germany by Peter Henlein in 1524.
Others appears in 1548 and more were produced in Switzerland and England
after 1575. At this time the main problem was the driving mechanism.
Typically, weights were used, which made portable watches impractical,
but it was a period of great advancement and innovation. The first
movements were made of steel, then later brass. They had no balance
springs and were notoriously inaccurate. The watches had only an hour
hand and had to be wound twice daily. Soon the spiral leaf mainspring
appeared, the greatest innovation at the time as it allowed long-term
power without weights. Because of a difference in timing between the
long arcs and the short arcs, accuracy could only be improved by using a
limited portion of the mainspring. Germany produced a watch with a cam
at the end of a barrel arbor to compensate for variations in spring
tension, but it was the English and French solution to use the
fusee. This stopped the watch during winding to prevent over
oscillation of the balance wheel. Additional stops were included as
regulators.