Re: Where are the others?
> Were they just very few of these?
Definitely. It's a terribly complicated device, hand-made to order, and must have cost a fortune, so I guess there were never more than a dozen made, it at all. There is a distinct possibility it was an unique object built for somebody.
If they knew how to do gears, why wouldn't there be a lot of simpler mechanisms like clocks and stuff? I think people at that time simply didn't realize the potential. After all they had also invented a kind of steam engine and didn't try to put it to any use either: Too soon, both were solutions to problems which hadn't yet cropped up (precise clocks were required for ocean navigation, steam for mines and large scale industry).
Besides, even if there were more geared devices, they are quite fragile and this one only survived because it was dug in marine sediment and left alone for millennia. Those on dry land would suffer much more damage and their pieces would had been recycled, or at least dispersed and deformed beyond recognition in the following 20 centuries.