Praktiflex FX SLR Film Camera with Waist Level Viewfinder, Zeiss Jena Tessar f3.5 50mm Lens, 105mm Wiesbaden Lens, Leather Case, and Filters The Praktiflex is a 35mm SLR film camera, manufactured by Kamera-Werkstätten VEB Niedersedlitz, (KW) Dresden, former East Germany and produced between 1939-49. KW was the third manufacturer to introduce a 24×36 SLR camera; only the Kine Exakta and the Russian Sport preceded it.
Also, the Praktiflex was the world's first small-format SLR camera with a returnable mirror and with a screw mount for interchangeable lenses. Its successor, the Praktica, became a very long and successful series of models. The Praktiflex has a special 40mm in diameter screw thread lens mount, and takes only Praktiflex lenses. The 42mm thread mount became available from about 1947, and was thus initiated by this manufacturer. This lens mount became practically an universal industry standard, until about 1975 when the need for increased exchange of information between camera and lens made the bayonet mount a more practical arrangement.
There are many models and variants of the Praktiflex. They could be divided two main generations.  The first generation includes pre-WW2 models and the second generation includes post-WW2 models. Produced between 1939-46 Lens: offered with various brand's lenses  Mount: M40x1 screw type Focusing: via condenser type ground-glass focusing screen Shutter: horizontal-run rubberised cloth-blind type shutter speeds: 1/25-1/500, +B Shutter release knob: on the top of the camera Mirror: not instant return, raises by pressing the release button. Shutter releases only when the mirror is raised. Viewfinder: Waist-level view finder with condenser type ground-glass focusing screen (Stevens Screen), fixed, w/ Magnifier and eye level sports finder There are some variants with special coloured leatherette like red, blue, gray. Some variants have no strap lugs and some variants have strap knobs