For some reason, I just love stories like this (Standard disclaimer: NYT article, you may need registration to read, I don't know how long it will be available "for free"). Another article about the same topic is here. That article suggests it may have been a sort of early calculator - that it could be used to multiply and divide.

It's about the Antikythera Mechanism, a mysterious group of gears and wheels found in a Greek shipwreck - it's suggested it may have been an early (like 80 B.C. early) computer of sorts. Wikipedia also has information on it.

Perhaps it was merely an astrolabe or some such thing. But I love stories that remind us that the ancients were not as technologically backwards as people like to think they were. (I'm also intrigued by the legend of the Babylonian "batteries").

(I also just like the name, "Antikythera Mechanism." It sounds like something out of a sci-fi or fantasy novel. Like, the Antikythera Mechanism is what could repel an alien invasion or provide an invisible force field around a walled city...)

Part of it is I love the idea of a mystery - we don't really totally truly know how or why these things were used. (Or in the case of the Baghdad "batteries," if they were really actually an electrical device). There's a certain romance to things like that for me - much more so than something that's cut and dried and more or less clear what it's for.

(I loved David Macauley's "Motel of the Mysteries" when I was a child. It kind of riffs on the idea that we may not know the actual purpose of ancient artefacts and so we may have the interpretation quite wrong. There's a very funny drawing in there of the "archaeologists" demonstrating "ceremonial headdress" of the USonians...and they have the toilet seats on their heads)

I also love the idea of some guy, somewhere, thousands of years ago, making something out of brass - the whole craftsmanship thing. (I also love the idea of the "difference engine" and the other older clunkier sorts of "made things" or "thinking machines." I wonder at what computers today would look like if their design was informed by a more Victorian sensibility (rather than the more modern, utilitarian one). Would they have brass filigree on them? Would the maker's name be in elaborate script? Would they be enclosed in cages that hung on the wall? Would "portable computers" have been in elaborate rucksacks or in picnic-basket-like conveyances?

I think that would be an interesting design contest: design a computer case-and-monitor set up as if you were someone from an earlier period of history, or if you were trying to break free of the black/beige rectangle model.