The device, housed in the remains of a 340-millimetre (13 in) × 180-millimetre (7.1 in) × 90-millimetre (3.5 in) wooden box, was found as one lump, later separated into three main fragments which are now divided into 82 separate fragments after conservation works.
Four of these fragments contain gears, while inscriptions are found on many others.
The mechanism was merely a lump of corroded bronze and wood at the time and went unnoticed for two years, while museum staff worked on piecing together more obvious statues.
On , archaeologist Valerios Stais found that one of the pieces of rock had a gear wheel embedded in it.
The knowledge of this technology was lost at some point in antiquity, and technological works approaching its complexity and workmanship did not appear again until the development of mechanical astronomical clocks in Europe in the fourteenth century.
All known fragments of the Antikythera mechanism are kept at the National Archaeological Museum in Athens, along with a number of artistic reconstructions/replicas of how the mechanism may have looked and worked.
Soon afterward it fractured into three major pieces.
Other small pieces have broken off in the interim from cleaning and handling, and still others were found on the sea floor by the Cousteau expedition.
Of the 82 known fragments, seven are mechanically significant and contain the majority of the mechanism and inscriptions.
Another theory suggests that coins found by Jacques Cousteau at the wreck site in the 1970s date to the time of the device's construction, and posits that its origin may have been from the ancient Greek city of Pergamon, Rhodes was a busy trading port in antiquity and a centre of astronomy and mechanical engineering, home to astronomer Hipparchus who was active from about 140 BC to 120 BC.
The mechanism uses Hipparchus's theory for the motion of the moon, which suggests the possibility that he may have designed it or at least worked on it.
There are also 16 smaller parts that contain fractional and incomplete inscriptions.
The main fragment contains the majority of the known mechanism.