John Harrison, English Inventor
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John Harrisons First Sea Clock
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Aztec Calendar
Getty Research Institute
Harrisons First Marine Timekeeper
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Sundial
Dennis D. Potokar
Skeleton With Hourglass, 16th Century
Wellcome Images
Huygens Marine Clock
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John Harrisons First Sea Clock #2
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John Harrison, English Inventor #1
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Pocket Watch
Robert Wilken
Huygens Marine Clock #2
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Aztec Calendar Wheel
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John Harrisons First Sea Clock #3
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