I am the proud owner of a Curta Type I calculator. These devices are probably the coolest devices ever made. If you don’t know about the Curta, click on this link to read the Wikipedia entry about them.
The Curta Type I that I own has serial number 54798, and I bought it on eBay from some guy in France. It works well, and is truly a remarkable little machine.
This page at Curtamania.com has the stats on my Curta, as well as some pictures from it’s previous owner.