The Zeiss Ikon Tenax II came to market shortly before World War II, and like a number of other Zeiss Ikon cameras, production did not resume after the cessation of hostilities.
The Tenax II is a bit of an oddity among Zeiss Ikon cameras. It takes a square photo (24mm x 24mm), thereby eliminating any need to rotate the camera for vertical shots.
Reportedly, it was created in response to the popularity of the motor-driven Robot cameras, which also produced a square photo of identical dimensions.
The lever to the left of the lens in the photo above is used to advance the film and tension the shutter.
Often seen with the Tessar lens, my camera has an interchangeable uncoated f/2.0 4cm Sonnar. Also offered were a wide-angle and at least two telephoto lenses, but both are rarely seen today.
The shutter release is in the usual Contax-style position -- the center of a dial, though in this case, it's the frame counter, which goes to 49. And again like a Contax, the back is removed to load and unload film. You can use either a standard 35mm cartridge and Zeiss Ikon film spool or the Zeiss Ikon film cartridges that you preload with film.
The rotating wedge prism rangefinder works very well with this lens, and the total focusing range is a short 30-degree rotation of the lever under the lens. The lever on the side is used to select the shutter speed from 1-1/400 plus B. The top-mounted spring-loaded tab is for removing the lens.
Rewinding the film is accomplished using the flip-up key that is a smaller version of the Super Ikonta film advance lever. Better than a knob, slower than a crank.
In the tradition of other fine Zeiss Ikon cameras, the Tenax II is solidly built with attention to detail and excellent workmanship. The size of the camera is a real plus, because I can slip it into my backpack or bag.
The Sonnar lens is very sharp with good contrast. As with all uncoated lenses, use reasonable care to avoid lens flare.