OK, I'm on a real computer now.
I get the impression that the first Contax I model was rushed to market. The rangefinder arm rides along the barrel of the lens helical, and it's a bit of a bumpy ride, meaning that the secondary image does not move smoothly.
The tab for the lens lock is too thin on my camera, allowing a lens to unlock itself. As I mentioned, there are no slow speeds, and it requires to much effort to advance the film and tension the shutter. It uses mirrors in the focusing system, and the secondary image is rather dim, despite careful cleaning of all components. Yes, I was very careful with the semi-gilded mirror.
The later model that I have, which has slow speeds, is a better camera - more refined, as I mentioned earlier in this thread. Everything seems more positive. I think this model uses prisms in the focusing system, and the secondary image slides smoothly to and fro. Lenses lock securely, and it just seems like a better made camera.
I need to replace the shutter straps -- the old ones gave way about six months ago. It's a shame, because this camera came with a clean and very beautiful nickel and black f/1.5 5cm Sonnar, which of course can be used with any other Contax. I like the idea of using the very classic Sonnar with its original camera.