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Antikythera Mechanism was found in a shipwrecked Roman vessel in the Mediterranean Ocean around 1900. Some experts at think it an astronomer's tool, calculating the position of the planets, moon and sun and was made about 100 B.C. An x-ray of the mechanism, revealed it to be complex, containing a sophisticated differential system of 30 to 70 gears.

Antikythera Mechanism reproduction at the American Computer Museum