I did some research into the Curta mechanical calculators mentioned in PR and have found quite a bit of information on them (they're even featured in a recent Scientific American article). I've uploaded a picture to the tribe's image archive. A beautiful example of form following function.

I'm currently trying to find out how one would go about acquiring one of these devices. I understand that they are hard to come by collector's items, but if anyone has any information I would love to hear it.