It's a wonderful piece of engineering indeed, but not the first one. Gears were used long before that (http://www.nptel.iitm.ac.in/courses/IIT-MADRAS/Machine_Desig...), as early as 2600 BC for opening doors, lifting water and measuring distances. Archimedes used gears for all kind of stuff in 330 BC (See http://www.mlahanas.de/Greeks/ArchimedesGears.htm)

An explanation for that fact that so few devices remain that a record of history seems to be missing, could be that they were made of metals (copper, bronze, etc) which were quite precious in that time, so the devices probably got recycled. Image that, some warrior smelting a few antikythera machines to forge a sword!