The Rapid is a bakelite reflex box camera that was made in Germany in 1950. Some were made without the strap, and there was also a less common version with a finder hood.
At the bottom there are three levers. The first one lets you choose one of two apertures, the second one lets you choose whether to use a built-in filter, and the third lets you select "instant" or "bulb" shutter speeds.
This example has a torn strap and some chips in the body, but I like the design and the price was right!