Thanks everyone. I finally got the camera in my hands and spent a bit of time playing with all the pieces. It all makes sense, except for the aperture setting. There are shutter speed markers, but no aperture markers. Plus the 'lever' that adjusts the aperture doesn't step, but slides smoothly, so I don't quite understand how to set aperture.

The lens is a Carl Zeiss Jena Tessar 6.3/210. I did a quick google search, but didn't really find anything useful. Am I missing something right in front of my face? I'd appreciate any help the APUG world can provide.